From: "Paul Heelis" Subject: New chemistry jobs vacancy site To
Subject: Re: ORGLIST: propyphenazone
Yüklə 2,96 Mb.
|
Subject: Re: ORGLIST: propyphenazone Look in the Merck Index. Herb Hedgecock __________________ Date: Mon, 20 Mar 2000 09:39:28 -0800 From: Jim Sims Subject: ORGLIST: propyphenazone The structure is in the Merck Index, 12th ed. #8056. Professor Jim Sims Department of Plant Pathology University of California, Riverside Riverside, CA 92521 Voice: 909 787 4127 FAX 909 787 4294 __________________ Date: Tue, 21 Mar 2000 13:52:36 +0100 From: "Schuit, ing. R.C." Subject: ORGLIST: Propyphenazone structure I got over 25 reactions and nwo I can probably dream the structure. Thanks! Next time I will look in the Merck Index and www.chemfinder.com. Robert __________________ Date: Tue, 21 Mar 2000 18:45:59 -0500 (EST) From: Christopher Paul Borella Subject: ORGLIST: Peptide bond formation from tfa salt Hello, I have a simple question, I have generated a TFA salt of a free amine, and want to couple it with an acid chloride insitu. I can't seem to find any reference for this reaction, there are plenty with HCl salts but not TFA. Would TEA be strong enough to break up this salt or do I need to do something else? A co-worker sugested exchanging it to the HCl salt by reacting with excess HCl, however my compound is not stable to those conditions (silyl protecting groups). I would appreciate it if someone could give me some advise as to how to solve this or at least point me to a reference. Thanks, Chris __________________ Date: Tue, 21 Mar 2000 17:31:53 -0800 From: "Chapman, Robert D" Subject: RE: ORGLIST: help!!!! Found it! Here's where to get it. B-) http://www.bl.uk/serials/ser-html/subset_GA-GD.html https://www.bl.uk/services/bsds/dsc/lexformn.html > ---------- > From: HU HONGKUN > Sent: March 20, 2000 12:46 AM > To: Multiple recipients of list orglist > Subject: ORGLIST: help!!!! >
> hello!Everyone! > I am a graduate in the Colllege of Chemic in the > Sichuan University. > I want someone find me a reference. > Galvanotechnik 1998,89(3),748-749 Eugen G.Leuze > verlag
> I can not find it here.It means a lot to me. So > please help me .Thanks a lot!!!! > you can contact me with email! >
> ===== > your sincerely Hu Hongkun __________________ Date: Tue, 21 Mar 2000 17:36:02 -0800 From: "Jack Kellum" Subject: ORGLIST: Re: Peptide bond formation from tfa salt Chris, There's no need to convert your TFA salt to the HCl salt. The critical factor is your choice of base. Whereas TEA would neutralize a TFA salt just as readily as an HCl salt, the problem lies in the fact that you're coupling with a highly activated carboxyl component. Your title said "peptide bond formation" so I assume that the two components you're attempting to couple are amino acids. In this case, using TEA with a amino acid chloride will likely result in formation of an N-carboxyanhydride or an oxazolone depending on the nature of your N protecting group. If the use of an amino acid chloride is your only choice, you'll want to employ a severely hindered tertiary amine base such as 2,6-di-tert-butylpyridine (Carpino, JOC, 1991, 2635).
for amino acids. An excellent review by Humphrey and Chamberlin appears in Chem. Rev., 1997, 2243.
I am an undergraduate student of chemistry, and this semester we have a special project on org.chem.laboratory. I will want to synthetize flavones, but I have not enough information about its synthesis and/or properties. I have find just one article at J.Chem.Edu (1980 57 220). I would appreciate anyone who can point me to good references on this. Thanks in advance for all responses. Salo K. __________________
Update Course & Conference on Heterocyclic Chemistry took place at the University of Gainesville, Florida from the 8th-11th of March. It was a highly successful event attended by students and chemists from all over the world. The success was such that we have already booked the conference for the year 2001 and 2002 at the same time during the spring break in March. Details about the course and lectures will be posted in the coming months on our web site. The ARKAT Project itself is coming along steadily. The first issue of Arkivoc appeared in February. The second issue will be made available by the second week of April, 2000.
join from our homepage) and participate in the development of this effort. It is our intention to have standards similar to JOC. However the internet permits us to cast a wider net. The two publications Arkivoc and Arkivod permit publication of both full papers and incomplete stories where compounds have been made and properly characterized. If any of you have ideas about offering a (commercial or informational) service to chemists, please contact me as we may be able to help you develop your concepts. We have a limited amount of funding for good projects. Best wishes, Paul Thind __________________ Date: Wed, 22 Mar 2000 16:31:54 +0100 From: Fredrik Thorstensson Subject: Re: ORGLIST: Synthesis Approach Hello Glen You could maybe try something like this Base
(NaH) Br or R2-Br HOBr, AcOH R1C(triple bond)-H ------------> R1C(triplebond)CR2 --------------> R1BrC(doublebond)CBrR2 Terminal alkynprotons are rather acidic and can be abstracted with base. You can make a halogenic addition on the alkynderivate. I think you can make it trans or cis depending on which conditions you use. NB. I have no practical experience of this. -- ************************ Fredrik Thorstensson LKPG University Sweden freto@ifm.liu.se ************************ Glen Brizius wrote: > Hello, all. I am trying to synthesize compounds with the following > molecular structure: RBrC(double bond)CBrR, where the halogens are > preferably trans to each other. An example would be > trans-2,3-dibromo-2-butene, which would have pendant methyl groups. > Ideally I'd like to have control over the identity of the alkyl groups, > which would hopefully come from commercially available precursors (alkyl > bromides, alcohols, aldehydes, etc). > > So far I've tried transforming trans-2,3-dibromo-1,4-dihydroxy-2-butene > into the 1,2,3,4-tetrabromo-2-butene with PBr3, followed by reaction > with alkyl Grignard reagents. However, this gives me a complex mixture > of (allylic rearranged) products. While I can make the dialkoxy > versions easily, they are not any good for my particular reaction, they > have to be alkyl. > > Does anyone have any experience in this type of synthesis that would > like to share? All opinions gratefully :) accepted via email. Thanks > in advance! > > Glen Brizius __________________ Date: Thu, 23 Mar 2000 10:19:00 +0100 From: Luis Fernando Garcia Alles Subject: ORGLIST: Stabilizing the enolate form Dear people, I am considering the synthesis of some analogue of PEP (phosphoenol pyruvate: Pi-O-C(=3DCH2)COOH) where the phosphoryl group (Pi) is missing. Initially, if we remove the Pi group from this molecule, the enolate form produced would immediately tautomerize to the ketone form (let us say pyruvate, CH3-COCOOH). However, I would like to design and synthesize some analogue where the enolate form would be more favoured, more populated than the ketonic form, that is, it would exist mainly as the following specie: R-CH=3DC(OH)COOH
to stabilize this enolic form??. Any idea will be wellcome... Well, thank you very much for whatever you might suggest me to do!!!
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D Luis Fernando Garc=EDa Alles, Ph.D. Departement f=FCr Chemie und Biochemie Universit=E4t Bern Freiestrasse 3 CH-3012 Bern, Schweiz Tel. ++41 (0)31/631 37 92 Fax ++41 (0)31/631 33 83=09 E-mail :garcia@ibc.unibe.ch =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
I am a veterinarian working on pharmacokinetics of sarafloxacin [fluoroquinolone] in fish farming. I need the physicochemical properties and synthesis of this chemical which it was impossible to find anywhere. I would be much grateful if anybody has some paper or document for it!
Sakis
Date: Thu, 23 Mar 2000 15:41:14 -0500 (GMT) From: "Research Scholars,tpr" Subject: Re: ORGLIST: Re: Peptide bond formation from tfa salt Hello Chris, i think you know, in peptide bond formation, if you're going to use amino acid chloride to couple with you will loose the chirality of the acid part. good luck palas gangopadhyay __________________ Date: Thu, 23 Mar 2000 11:53:07 -0500 From: David Gauthier Subject: Re: ORGLIST: Peptide bond formation from tfa salt Hi, I think that TEA will work, but you must find good references first. Try these : JACS (98) p.12783 Chem.Europ.J.En (99) p.79 Tet.(88) p.2359 Tet.(99) p.3511 JOC (99) p.4324 Good luck David Gauthier University of Sherbrooke
service. Please refrain from asking questions before attempting to find the answer on your own. This is a very simple question that can be answered in 5 min on any litereature search program. __________________ Date: Fri, 24 Mar 2000 20:19:14 +0200 (EET) From: Subject: ORGLIST: BuLi Dear Colleagues, I hope somebody can give me a good advice for my problem. I synthesized butyllithium by reacting BuCl with excess Li (seven hours boiling in dry hexane). Then I let the solid phase to settle and then I siphoned the solution with the argon pressure to the dry flask. The solution is clear. All the procedure was done in oven-dried apparatus with dry inert gas flow (Ar). But now I have a problem with the determination of the BuLi concentration. I did it twicely. 1. Firstly I hydrolyzed the aliquot of BuLi by some water and then I titrated it with HCl. I got 1.76M for the concentration. 2. Secondly I did the so named "double-titration". I react BuLi with benzylchloride in ether (five minutes for reaction). BuLi must react with PhCH2Cl and the impurities will remain (BuOLi, LiOH). Then I decomposed the mixture with water and titrated it with HCl. Now I got 0.60M for the impurities concentration and so only 1.16M for the BuLi concentration. Is it possible I have so many impurities in my reagent? (It means that air humidity and oxygen reacted with the product!) What do you think about such "double-titration method"????? Can I trust this method? Or can somebody advice me something better? All the reagents were pure and dry.
chloro-nitroso compounds? If so, what raccomandations would you give me for such analitical procedures? I am trying to detect some gem Cl-NO compounds obtained from short aliphatic beta-keto esters, having so far done some GC/MS runs, but gaining little reproducibility...(by the way, those comp. should be somehow fragile at normal condition for GC/MS, shouldn't they?) Any kind of suggestion is welcome! Thanks very much, andrea.
********************************************************************* Andrea Giordano tel. ICN: 06 - 90672-510/516 CNR- Ist. Chimica Nucleare fax. ICN: 06 - 90672512 Via Salaria km 29.300 C.P. 10 cell: 0349 - 7512467 00016 Monterotondo Stazione (Roma) Italia
>> Happiness is easy << ********************************************************************* __________________ Date: Fri, 24 Mar 2000 21:11:48 -0500 (EST) From: Christopher Paul Borella Subject: Re: ORGLIST: BuLi Well I'm not sure about the titration, I normally just titrate with di phenyl acetic acid. However, when we must prepare n-BuLi (normally we buy from aldrich except for very large scale) we sonicate for 3hr rather than heating. We found this normally gives quantitative conversion of the BuCl. The solution is then transfered via canula to remove the LiCl. Heating of the solution may be causing decomposition, or dimerization.
important factors needed for good quality alkyl lithium are : (a) The Li metal must be very finely dispersed. This done by heating Li shots in liquid paraffin in a 3-neck flask fitted with an outlet at the bottom and then vigorously stirring with a mechanical stirrer. (b) VERY slow addition of alkyl halide to the suspension of the dispersed metal (cyclohexane in the case of sec-BuLi and Petroleum ether in the case of n-BuLi). 4 drops in 15 seconds. (c)Addition of few pieces of Na for initiating the reaction.
all the solvents should be thoroghly dried. Our experience tells that commercially available Li dispersions are unsuitable. The dispersed metal is washed free of Liquid paraffin with pet.ether. For sec-BuLi overnight stirring is needed after the addition of sec-butylchloride. We do heat the mixture in the case of n-BuLi but Chris' suggestion of sonication is good. The preparation must be done under good care. Otherwise accidents are likely.Pressure must be released from time to time while the metal is dispersed.
is simple and reliable. The reference is :=20 W.G.Kofron and L.M.Baclawski, J.Org.Chem., 1976,Vol 41, 1879.
>important factors needed for good quality alkyl lithium are : >(a) The Li metal must be very finely dispersed. This done by heating Li >shots in liquid paraffin in a 3-neck flask fitted with an outlet at the >bottom and then vigorously stirring with a mechanical stirrer.
lithium metal between two clear plastic OHP slides and bash it flat with a hammer. Get someone to help you by slicing the lithium foil with a scalpel while you drop it with tweezers into your reaction vessel. Obviously the quicker you do it, the better.
Dept. of Chemistry University of Queensland Brisbane, Australia __________________ Date: Sun, 26 Mar 2000 23:26:41 -0800 (PST) From: Subject: ORGLIST: N-phenyl-p-nitrobenzohydroxamic acid Dear people, Can you tell me what is the melting point of N-phenyl-p-nitrobenzohydroxamic acid. Thanks.
A/Hafeez Mohamed. e-mail: ahafeez61@yahoo.com __________________ Date: Mon, 27 Mar 2000 14:12:32 +0200 From: Jonas Nilsson Subject: ORGLIST: Aminoacids Dear List Members Does anybody have the aminoacids, their structure/abbrevations/names/pKa and such collected in a nice sheet of paper that could be posted on the wall? Please send me a file. /jN
_____________________ _____________________ | Jonas Nilsson | | | |Linkoping University | | Telephone | | IFM | | --------- | | Dept. of Chemistry | | work: +46-13-285690 | | 581 83 Linkoping | | fax: +46-13-281399 | | Sweden | | home: +46-13-130294 | |_____________________| |_____________________| __________________ Date: Mon, 27 Mar 2000 17:55:37 +0530 (IST) From: Dr T A Pathak Subject: Re: ORGLIST: Aminoacids Structure/name/abbreviation of proteinogenic alpha-aminoacids without pKa values are available on page xiii of "Synthesis of optically active alpha-amino acids" by Robert M. Williams (Pergamon).
Dr. Tanmaya Pathak Tel: (020)-589 33 00 Organic Chemistry Division (Synthesis) 589 33 15/16 National Chemical Laboratory extn.2055/2073 Pune 411 008 (020)-589 31 53 Maharasthra Fax: (020)-589 31 53 India e.mail: pathak@ems.ncl.res.in ----------------------------------------------------------------------------- __________________ Date: Mon, 27 Mar 2000 14:42:01 +0200 From: Francesco Dondero Subject: ORGLIST: maleimide dear sirs, I'm a PhD student of biology and I have a biochemical question to tell you.
In brief, I have a protein rich in sulphydryls that I'd like to quantify by reaction with a specific compound having a great affinity for thiols. I must not use chemitry involving Ellman's reagent (2,2,DTNB) or similar thiol-disulphur exchange reagent, so I should try with maleimide. Does exist any maleimide that reacting with sulphydryls of proteins gives rise to a coloured compound, spectrophotometrically evaluable? I know that many maleimides gives rise to fluorescent compound, but I need a coloured one. best regards Francesco Dondero Universita' Piemonte Orientale 15100 Alessandria, Italy __________________ Date: Tue, 05 Jan 1904 04:20:08 +0200 From: Jacob Zabicky Subject: Re: ORGLIST: methyl cyclohexene from methyl cyclohexanone Dear Juana, Your question can have variuos replies, depending on who answers and on the point of view. A chemist dealing with reaction mechanisms may propose several steps, where only the slowest are in control of your results, but you cannot avoid passing through the fastest, lest your results differ from the desired ones.
you observe what are you putting in your reactor and what are you getting out of it. If you devise a contraption where starting from cyclohexanone and other reagents, you get methylcyclohexene whithout need of separating or adding other reagents at some intermediate stage, then you have what an organic synthesist may call a "one-step-reaction." This situation, however, need not be the best for the usual synthetic methods of organic chemistry, which are batch processes undertaken in a liquid matrix, between the normal melting and boiling points of the liquid phases. An industrial route may involve gaseous reagents continuously flowing over a multifunctional catalyst bed.
a route including the Grignard reaction and an intermediary tertiary alcohol, whether you isolate it or not. Whether you get an exo- or an endo-cyclic water elimination from the intermediate alcohol depends on the structure of the cyclic group. If you start from cyclohexanone you'll probably get 1-methylcyclohexene, however, if your starting ketone is cyclopentanone, your end product may be 1-methylenecyclopentane.
********************************************************************* Temporary address: Prof. Jacob Zabicky Tel.: +34 93 581 1401 Group de Fisica dels Materials II Fax.: +34 93 581 2155 Universitat Autonoma de Barcelona Private: 08193 Bellaterra (Barcelona) Tel.: +34 93 581 7485 Spain
********************************************************************* __________________ Date: Mon, 27 Mar 2000 11:49:46 -0800 From: "Chapman, Robert D" Subject: RE: ORGLIST: Aminoacids http://online.sfsu.edu/~trautman/amino/amino_prop.html > ---------- > From: Jonas Nilsson > Sent: March 27, 2000 4:12 AM > To: Multiple recipients of list orglist > Subject: ORGLIST: Aminoacids >
> Dear List Members > Does anybody have the aminoacids, their structure/abbrevations/names/pKa > and such collected in a nice sheet of paper that could be posted on the > wall? Please send me a file. > /jN >
> -- > _____________________ _____________________ > | Jonas Nilsson | | | > |Linkoping University | | Telephone | > | IFM | | --------- | > | Dept. of Chemistry | | work: +46-13-285690 | > | 581 83 Linkoping | | fax: +46-13-281399 | > | Sweden | | home: +46-13-130294 | > |_____________________| |_____________________| >
__________________ Date: Mon, 27 Mar 2000 12:09:34 -0800 From: "Chapman, Robert D" Subject: RE: ORGLIST: Aminoacids In addition to http://online.sfsu.edu/~trautman/amino/amino_prop.html also http://www.imb-jena.de/IMAGE_AA.html http://www.infobiogen.fr/services/deambulum/english/standards.html#AA http://www.public.iastate.edu/~pourel/lsci.html#sbiol Sometimes I pursue an occasional ORGLIST inquiry like this just to see if some expectedly common information is actually surprisingly unavailable from a simple Web search. But no surprise here. Robert D. Chapman, Ph.D. Chemistry & Materials Division (Code 4T4200D) Naval Air Warfare Center China Lake, CA 93555 USA
by CAS (http://info.cas.org/EO/ejourn2.html) you would find that many of them have been able to publish only a small number of papers every year. Online journal editors, do not give up. MOLECULES now continuously publishes "thick" issues this year. Its vol.5 issue 3 (March 2000, pages 200-636) just released has 437 pages (http://www.mdpi.org/molecules/list00.htm#new). We publish many more papers recently and publish very quickly after peer reviewing procedure. (A long list of referees who helped evaluating manuscripts will be published soon.) Contributions of manuscripts are welcomed. I would like to acknowledge that this is the achievements of the Assistant Editor Dr. Derek J. McPhee (e-mail: mcphee@mdpi.org) who carefully and promptly handled many manuscripts, and the Production Editor Dr. Andrey Gutnov (e-mail: gutnov@mdpi.org), who did layout and final pdf files generation. Could you please help us by listing our journal MOLECULES (http://www.mdpi.org/molecules/) on your website and recommend it to your colleagues?
Managing Editor, MOLECULES (ISSN 1420-3049) E-mail: lin@mdpi.org
Molecular Diversity Preservation International (MDPI) Saengergasse 25, CH-4054 Basel, Switzerland Tel. +41 79 322 3379, Fax +41 61 302 8918 E-mail: lin@mdpi.org http://www.mdpi.org/lin/ __________________ Date: Tue, 28 Mar 2000 19:21:54 +0900 From: Mitsuhiko FUJIWHARA
Subject: Re: ORGLIST: BuLi I think that double titlarion should be the most reliable, but I usually don't do that practice. What I do is 1,10-phenanthroline method. If you have access to "Lancaster" catalogue, there is the reference for this method. I quote only one reference here: J. Organomet. Chem. vol 9, 165 (1967). It's not so reliable, but quite convenient and enough for usual organic synthesis. It is said that we cannot use this method for MeLi.
Mitsuhiko FUJIWHARA, Ph.D. Fine & Aroma Chemical Laboratory Takasago International Corporation PGP-key http://www.asahi-net.or.jp/~bj9m-fjwr/index.html PGP FingerPrint [6087 4106 3402 2D84 489B 1A83 582B 7B82 F8EB 3590] __________________ Date: Tue, 28 Mar 2000 17:49:10 -0800 (PST) From: Eugene Leitl Subject: Orglist: free preprint service: Tetrahedron Letters online Free. Registration required (my chemweb ID worked). http://chemweb.com/tetfast/ __________________ Date: Wed, 29 Mar 2000 09:29:11 -0500 (GMT) From: "Dr. D.Basavaiah-(RS)" Subject: Re: Orglist: free preprint service: Tetrahedron Letters online Dear Friends: 1.I need a clean method for the allylic oxydation of limonene at c-10 position. I am aware of the Crawfords work (Limonene +n-BuLi/TMEDA complex followed by air oxydation). This method gave 15% impurity after Fractionating. Is there any better method. 2. Any method for deoxygenating allyl alcohols other than the following methods
1. TMSI 2. Barton-McCombe 3. Pyridine-SO3 4. DEAD/PPh3 5. CoCl2/KCN/KCl 6. Tungsten complexes 7. Electrochemical methods 8. BF3OEt2/NaBH4 Please give me the information within your experience, no matter whether it is published/unpublished. In case publishe, will you be so kind to give the literature reference? Thanks
Chary ************************************************************************** Research Scholar School of chemistry Telephone: 3010500 extn:4807 University Of Hyderabad Hyderabad- 500 046 India
************************************************************************** __________________ Date: Wed, 29 Mar 2000 11:05:57 +0200 From: Shu-Kun Lin Organization: MDPI (http://www.mdpi.org) Subject: Orglist: MDPI news release: Int. J. Mol. Sci. (http://www.mdpi.org/ijms/) Vol. 1, 2000 Issue 1 Released (Exculse me for sending to many mailing lists) MDPI launched one more new journal International Journal of Molecular Sciences (ISSN 1422-0067) at the http://www.mdpi.org/ijms website. The background regarding IJMS is at http://www.mdpi.org/ijms/htm/i1010003.htm.
and unique userID and password from ijms_request@mdpi.org (put "free subscription" as the subject title and your name and address in the text of your e-mail). A "Call for Papers to the IJMS" message as a pdf can be downloaded at http://www.mdpi.org/ijms/ijmsadvert.pdf. Shu-Kun -- Dr. Shu-Kun Lin Molecular Diversity Preservation International (MDPI) Saengergasse 25, CH-4054 Basel, Switzerland Tel. +41 79 322 3379, Fax +41 61 302 8918 E-mail: lin@mdpi.org http://www.mdpi.org/lin/
when the commercial 1H-tetrazole dissolved in solution (eg. dioxane), but what the percentum for 1H-tetrazole and 2H-tetrazole? 2. Where can I find the information of the pKa value about the proton in heterocycle, such as tetrazole, imidazole, pyrazole, triazole and so on?
yanch@ifm.liu.se __________________ Date: 29 Mar 2000 14:38:40 -0800 From: Juana L Subject: ORGLIST: tetradecanol Hello I will want to know if somebody knows the b.p. of 2-tetradecanol. I sintetized it(by Grignard reaction), but I have not find any reference of that physical constant. Thank you very much for your help
TITLE Dissociation constants of organic bases in aqueous solution. PUBLISHER London : Butterworths, 1965. DESCRIPT 473p : ill ; 26cm. NOTE Published as a supplement to Pure and Applied Chemistry. BIBLIOGRAPHY Includes bibliography. NOTE At head of title: International Union of Pure and Applied Chemistry. Analytic Chemistry Division. Commission on Electroanalytical Chemistry. SUBJECT Dissociation. Electrochemistry. Chemistry, Organic -- Tables. This reference has many pKa values for heterocyclic bases. There is also a supplement published in the 1970's, but I could not find the record.
>the information of the pKa value about the proton in heterocycle, such as >tetrazole, imidazole, pyrazole, triazole and so on?
Richard
Senior Lecturer School of Pharmacy Phone: INT + (617) 3365-3179 University of Queensland Fax: INT + (617) 3365-1688 St Lucia QLD 4072 richard@pharmacy.uq.edu.au AUSTRALIA http://www.uq.edu.au/pharmacy/rprank.html __________________ Date: Thu, 30 Mar 2000 14:50:34 +0200 From: Eva Horn Moeller Subject: Re: ORGLIST: two questions Dear Yantao (and others)... An extremely good review on all aspects of the basicity and acidity of azoles is that of J. Catalan in "Advances in Heterocyclic Chemistry", vol. 41, pp. 187-274. MANY tables with pKa values for a lot of azoles - and more... Best regards, Eva
I have large quantitiy of colored THF that has to be recovered. Before distillation I want to make sure that the peroxide content is within 40ppm limit. In the standard test, KI/HCl, we do not get quantitative information. Also, I wonder how to get rid of the peroxide, if the peroxide limit is beyond the limit. We cannot use alumina since it leads to enormous loss of solvent.
I thank you in advance for the information Krish M. Chary ************************************************************************** Research Scholar School of chemistry Telephone: 3010500 extn:4807 University Of Hyderabad Hyderabad- 500 046 India
************************************************************************** __________________ Date: Fri, 31 Mar 2000 10:05:23 +0530 (IST) From: A De Subject: Re: ORGLIST: How to estimate peroxide content in colored THF Calcutta, March 31, 2000 Keep it over good quality KOH. You may have to repeat a couple of times. When the colour is gone do the KI/HCl test and finally carry out the standard benzophenone ketyl procedure. Cheers Asish
Professor Asish De Dept. of Organic Chemistry Indian Association for the Cultivation of SCience Calcutta - 700 032 INDIA On Thu, 30 Mar 2000, Dr. D.Basavaiah-(RS) wrote: > > Dear Colleagues: > I have large quantitiy of colored THF that has to be recovered. Before > distillation I want to make sure that the peroxide content is within 40ppm > limit. In the standard test, KI/HCl, we do not get quantitative > information. > Also, I wonder how to get rid of the peroxide, if the peroxide limit is > beyond the limit. We cannot use alumina since it leads to enormous loss of > solvent. > I thank you in advance for the information > Krish M. Chary >
> ************************************************************************** > Research Scholar > School of chemistry Telephone: 3010500 extn:4807 > University Of Hyderabad > Hyderabad- 500 046 > India
> > e-mail: dbscrs@uohyd.ernet.in > > ************************************************************************** APRIL 2000 Date: Sun, 2 Apr 2000 08:19:39 -0500 (GMT) From: "Dr. D.Basavaiah-(RS)" Subject: Re: ORGLIST: How to estimate peroxide content in colored THF Dear Ashish: Thank you for the reply. But, there are some reports of serious explosions when THF is treated with KOH.(See Burfield JOC, 1982, 47, 3821-24) (The process is actually deflagration!) Are you sure that good quality THF will remove peroxides safely? Also, at an industrial level, use of benzophenone/ketyl is not viable, so we use very good quality molecular sieves for drying. Thank you once again and keep in touch Krish
Research Scholar School of chemistry Telephone: 3010500 extn:4807 University Of Hyderabad Hyderabad- 500 046 India
************************************************************************** __________________ Date: Sun, 02 Apr 2000 20:24:25 +0500 From: "G.Sundararajan" Subject: Re: ORGLIST: Synthesis Approach Hi Glen! You are way ahead of everyone else! check the date set on your computer! Sundar At 01:17 AM 4/18/00 -0400, you wrote: Hello, all. I am trying to synthesize compounds with the following molecular structure: RBrC(double bond)CBrR, where the halogens are preferably trans to each other. ......................................
Dr. G. Sundararajan Office Home Ph: 0091-44-445 8254 445 9254 Department of Chemistry D-7-11, Banyan Avenue
__________________ Date: Sun, 02 Apr 2000 15:56:13 -0400 From: Merlin Subject: ORGLIST: Recent news about Taxol There was a recent news flash about Taxol (PaclitaxelÆ) being found in Hazelnuts(?) Anyone else hear this? If so, please cite your source(s). Thank you in advance. Cheers! -- George D. 'Merlin' McCallion, Research Chemist Department of Anesthesiology The Children's Hospital of Philadelphia Post Office Box 143 Bala-Cynwyd, PA 19004-0143 Office: 1.215.590.6894 Fax: 1.215.590.4554 Email: medchem@home.com
-- George D. 'Merlin' McCallion, Research Chemist Department of Anesthesiology The Children's Hospital of Philadelphia Post Office Box 143 Bala-Cynwyd, PA 19004-0143 Office: 1.215.590.6894 Fax: 1.215.590.4554 Email: medchem@home.com
in the News section (3/30/2000) at CombiChem Lab (www.combichemlab.com). Hope it helps. Guillermo. -----
Guillermo A. Morales E-mail: morales@combichemlab.com Website: www.combichemlab.com
point of view. A chemist dealing with reaction mechanisms may propose several steps, where only the slowest are in control of your results, but you cannot avoid passing through the fastest, lest your results differ from the desired ones.
you observe what are you putting in your reactor and what are you getting out of it. If you devise a contraption where starting from cyclohexanone and other reagents, you get methylcyclohexene whithout need of separating or adding other reagents at some intermediate stage, then you have what an organic synthesist may call a "one-step-reaction." This situation, however, need not be the best for the usual synthetic methods of organic chemistry, which are batch processes undertaken in a liquid matrix, between the normal melting and boiling points of the liquid phases. An industrial route may involve gaseous reagents continuously flowing over a multifunctional catalyst bed.
a route including the Grignard reaction and an intermediary tertiary alcohol, whether you isolate it or not. Whether you get an exo- or an endo-cyclic water elimination from the intermediate alcohol depends on the structure of the cyclic group. If you start from cyclohexanone you'll probably get 1-methylcyclohexene, however, if your starting ketone is cyclopentanone, your end product may be 1-methylenecyclopentane.
>Hello
>I will like to synthetize methyl cyclohexane from methyl cyclohexanone. I >will like to know if it is posible to do in just one step.I would greatly >appreciate anyone who can point me to good references on this, because I >have searched in some books with no success. >Thank you > >Juana L. ********************************************************************* Temporary address: Prof. Jacob Zabicky Tel.: +34 93 581 1401 Group de Fisica dels Materials II Fax.: +34 93 581 2155 Universitat Autonoma de Barcelona Private: 08193 Bellaterra (Barcelona) Tel.: +34 93 581 7485 Spain ********************************************************************* __________________ Date: Mon, 03 Apr 2000 10:55:37 +0200 From: Jacob Zabicky Subject: Re: ORGLIST: Synthesis Approach Hello Glen, Just a couple of hints. The first reactions of olefins children learn about is halogen, and in particular bromine, addition. This sounds decievingly simple. The best is to heed the advise in Organic Synthesis aut the preparation of 1,2-dibromocyclohexane from,cyclohexane, namely, freshly distilled olefin, cooling, and careful addition of the bromine. If you use your olefin from the bottle, it may contain peroxides and your product ends up as a fuming mess. PROTECTION FROM LIGHT, wrapping your reacting vessel with Al foil, may also contribute to a purer product. Jacob >Hello, all. I am trying to synthesize compounds with the following >molecular structure: RBrC(double bond)CBrR, where the halogens are >preferably trans to each other. An example would be >trans-2,3-dibromo-2-butene, which would have pendant methyl groups. >Ideally I'd like to have control over the identity of the alkyl groups, >which would hopefully come from commercially available precursors (alkyl >bromides, alcohols, aldehydes, etc). > >So far I've tried transforming trans-2,3-dibromo-1,4-dihydroxy-2-butene >into the 1,2,3,4-tetrabromo-2-butene with PBr3, followed by reaction >with alkyl Grignard reagents. However, this gives me a complex mixture >of (allylic rearranged) products. While I can make the dialkoxy >versions easily, they are not any good for my particular reaction, they >have to be alkyl. > >Does anyone have any experience in this type of synthesis that would >like to share? All opinions gratefully :) accepted via email. Thanks >in advance! > >Glen Brizius ********************************************************************* Temporary address: Prof. Jacob Zabicky Tel.: +34 93 581 1401 Group de Fisica dels Materials II Fax.: +34 93 581 2155 Universitat Autonoma de Barcelona Private: 08193 Bellaterra (Barcelona) Tel.: +34 93 581 7485 Spain ********************************************************************* __________________ Date: Tue, 4 Apr 2000 10:04:49 +0200 From: Sats Somera - Merebank Subject: ORGLIST: Replacement of Titanium trichloride Colleagues, I am trying to determine a replacement for Titanium trichloride, a chemical that is presently being used as a coating of raw sugar, which seems to add depth of colour and a sparkle to the sugar crystals. I was wondering as to whether any one has done tests with some other additives and received similar results?
Project Development Manager Tel : +27 31 - 4507700 (general) : +27 31 - 4507837 (direct) : +27 83 - 7794440 (mobile)
New Product Development P.O. Box 31003 Merebank
South Africa 4059
Date: Tue, 4 Apr 2000 19:45:02 -0500 (GMT) From: "Dr. D.Basavaiah-(RS)" Subject: ORGLIST: Oxidation of limonene at C-10 Dear Colleagues: I want a simple procedure for the synthesis of c-10 hydroxy Limonene. I am aware of the crawfords work (i.e. N-BuLi-Tmedaf-limonene-aireal oxydation/reduction procedure/) But we are getting some impurity in this process. I would like to know the problems associated with its synthesis by any body who has done this reaction. If any body can suggest a more convenient method, it is fine. I thank you in advance for the information Krish
- in real time - on the Web - in 3D - for FREE! New Features: ----------------------------------------------------------------- - Another 25,000 molecular models have been added. We now have over 200,000 molecular models on-site.
No more *Site not responding* messages - hopefully! - Expanded Model Options services ------------------ WebMolecules News Sponsor ------------------ www.chemjobs.net Go to http://www.chemjobs.net for chemistry jobs worldwide - FREE e-mail bulletin of current openings - FREE job vacancy postings
Molecule of the Month ----------------------------------------------------------------- Taxol (paclitaxel) http://www.webmolecules.com/cgi-bin/webmolpage.cgi?taxol.m3d Formula: C47 H51 N O14 Weight: 853.920(1) g/mol Taxol is in the news again. Dr./Sr. Angela M. Hoffman of the University of Portland, Oregon, while researching a cure for a blight that kills hazelnut trees discovered that the trees and their nuts contain paclitaxel (Taxol).
the heretofore only known natural source of paclitaxel. She said this is the only reason she recognized the chemical and the potential significance of the discovery. Hoffman announced her discovery at the recent national meeting of the American Chemical Society in San Francisco. Taxol(R), which is manufactured by Bristol-Myers Squibb, is used to treat breast and ovarian cancers, Kaposi's sarcoma, and some forms of lung cancer. It is also under investigation for treating psoriasis, polycystic kidney disease, multiple sclerosis and Alzheimer's disease.
is currently very complex and therefore too costly to be practical. ------------------ WebMolecules News Sponsor ------------------
science communication on the Web from award winning science writer David Bradley. http://www.sciencebase.com/
Suggestion Box ----------------------------------------------------------------- Is there a new feature you would like to see at WebMolecules? Let us know at: newideas@webmolecules.com Recent Upgrades and New Features ----------------------------------------------------------------- - Expanded molecular display controls - NSC ID's supported for Bookmarking and Searching - The WebMolecules server/network completely upgraded. - You can search the entire WebMolecules Library by formula. - SEARCH can now accept formula strings with elements in any order. - Email Models to Friends. Use the Email-a-Model link. - 100's of large macro-structures have been added. - New Visitor Uploads are available in Category 28.0 - Support for both Chime and VRML plug-ins - For performance reasons, large molecules (>150 atoms) are available for the Chime viewer only. - Mirror sites for the VRML plug-ins have been added. See: http://www.webmolecules.com/vrmlint.shtml - Mirror sites for the Chime plug-in has been added. See: http://www.webmolecules.com/chimeint.shtml - Resizable viewing window - Support for uploads and model requests - Improved support for bookmarks - 3D coordinate downloads (M3D, MOL, PDB) ----------------------------------------------------------------- WebMolecules.com is a FREE, sponsor-supported site. Designed for the 3D visualization of molecules, it contains over 200,000 molecular structures in 3D.
Our ** TOP 2000 ** includes molecules of commercial value, educational importance, and of topical interest. It is indexed by formula and category and is also fully searchable. Our TOP 2000 models include: - Top 100 pollutants - Top 100 commercial chemicals - Top 200 pharmaceuticals - Common valence geometries - Common orbital configurations WebMolecules.com is great for student and classroom use. ----------------------------------------------------------------- KNOW SOMEONE WHO MIGHT ENJOY WEBMOLECULES?
If you received this issue from a friend and would like to receive information directly, you can join our mailing list by clicking the Free Newsletter link at: http://www.webmolecules.com/newsletter.shtml
http://www.webmolecules.com/newsletter.shtml To cancel this newsletter, send an email to: unsubscribe@webmolecules.com ----------------------------------------------------------------- Enjoy,
----------------------------------------------------------------- First visit? Use: http://www.webmolecules.com/setup.shtml
__________________ Date: Wed, 05 Apr 2000 10:29:38 +1000 From: Paul Handley Subject: ORGLIST: Oxidation of limonene at C-10 >Dear Colleagues: >I want a simple procedure for the synthesis of c-10 hydroxy Limonene. >I am aware of the crawfords work (i.e. N-BuLi-Tmedaf-limonene-aireal >oxydation/reduction procedure/) But we are getting some impurity in this >process. I would like to know the problems associated with its synthesis >by any body who has done this reaction. If any body can suggest a more >convenient method, it is fine. >I thank you in advance for the information >Krish
alcohol from the deprotonation step. For a more convenient method see US patent 5574195 Chastain et al. November 12, 1996. Same deprotonation, react the allyl anion with trimethyl borate, oxidise the adduct with aq. H2O2. Yield reported is 65-75%, no limonene dimers. I have not tried this method myself. I posted this reference previously and I assume you did not receive it, my apologies if you did. Good luck,
Dept. of Chemistry University of Queensland Brisbane, Australia __________________
I have an chiral compound which is based on the 1R,2R-trans-1,2-cyclopropanedicarboxylate. I need a good way to see if a have got some racemization in this cyclopropane-ring. I have optical rotation so the racemization is not complete at least. I see no trace of the cis compound, probably due to it's more hindred configuration. I might however have som of the other trans (1S,2S) compound. I was thinking about using the Eu(hfc)3 chiral NMR-shift ligand, which we have inhouse. Has anybody any experience or good reference on this. Most of what I seem to find is published in Journals we don't have. A good reference or a review article would be great. The cyclopropane-dicarboxylic acid is derivitized with one methyl ester and one achiral amine. Would the Eu(hfc)3 shift the methyl ester protons for instance? Can I use protic solvent with the Eu(hfc)3 (MeOH-d5). How much of the shift-reagent should I use. note Eh(hfc)3=Europium tris[3-(heptafluoropropylhydroxymethylene)-(+)-camphorate] [CAS 34788-82-4]
jN
_____________________ _____________________ | Jonas Nilsson | | | |Linkoping University | | Telephone | | IFM | | --------- | | Dept. of Chemistry | | work: +46-13-285690 | | 581 83 Linkoping | | fax: +46-13-281399 | | Sweden | | home: +46-13-130294 | |_____________________| |_____________________| __________________
mine. These present a novel way of detecting the presence of racemates in chiral structures without resorting to chiral lanthanide shift reagents, although it should really be thought of as complementary to such spectroscopic solution techniques.
II. Peak shape analysis and deconvolution of overlapping endotherms in differential scanning calorimetry of chiral mixtures. Int J Pharm, 86, 211-219, 1992. Elsabee, M. and PRANKERD, R.J. Solid state properties of drugs. Part III. Differential scanning calorimetry of drugs existing as racemic solid solutions, racemic mixtures and racemic compounds. Int J Pharm, 86, 221-230, 1992. PRANKERD, R.J. and Elsabee, M. Thermal analysis of chiral drugs. The DSC behaviour of mixtures of ephedrine HCl and pseudoephedrine HCl enantiomers. Thermochimica Acta, 248, 147-160 1995.
be quantitative in the right circumstances. The one essential criterion is that the chiral compound must have a defined melting point with minimal or no decomposition. If it does not meet this criterion, then the method cannot be used. We have used it with substances with single chiral centres and with diastereomers. If you have difficulty in accessing these references, then I can send you reprints on request. Regards Richard
>I have an chiral compound which is based on the >1R,2R-trans-1,2-cyclopropanedicarboxylate. I need a good way to see if a >have got some racemization in this cyclopropane-ring. > >I have optical rotation so the racemization is not complete at least. I >see no trace of the cis compound, probably due to it's more hindred >configuration. I might however have som of the other trans (1S,2S) >compound.
Senior Lecturer School of Pharmacy Phone: INT + (617) 3365-3179 University of Queensland Fax: INT + (617) 3365-1688 St Lucia QLD 4072 richard@pharmacy.uq.edu.au AUSTRALIA http://www.uq.edu.au/pharmacy/rprank.html __________________
My name is Alexandro Pereira da Silva. I am a student chemistry in Universidade Federal do Rio de Janeiro/Rio de Janeiro - Brasil. I am writing because I am needing of the synthesis of the OXALYL CHLORIDE (ETANEDIOYL DICHLORIDE). Help me, please. P.S.: Sorry, I do not speack english but I am studing english now. Alexandro Pereira da Silva Student Chemical and technical chemistry in the Organic Departament Process in the UFRJ - Brasil. __________________ Date: Fri, 7 Apr 2000 09:32:00 -0500 (GMT) From: "Dr. D.Basavaiah-(RS)" Subject: Re: ORGLIST: Sinthesis oxalyl chloride dear friend u can prepare the oxaloyl chloride from anhydrous oxallic acid and phosporous pentachloride in 1:2 ratio and distill the reaction mixture collect the fractions at 70-80 C ,boiling point of the oxalyl chloride is 64 C. avoid the POCl3 fractions to come out.(bpt.106C) yield :about 50-60% ************************************************************************** Research Scholar School of chemistry Telephone: 3010500 extn:4807 University Of Hyderabad Hyderabad- 500 046 India
************************************************************************** __________________ Date: Fri, 7 Apr 2000 18:29:18 +0200 From: "Yantao Chen" Subject: ORGLIST: tetrazole Dear Chemists: Recently I run the reaction of N-protected Tetrazole with n-BuLi in THF at -78 degree, and then the resulting mixture was quenched with electrophilic reagents. Trust me, I run the right operation procedure, but I can not get the right compounds. Anyone has some chemistry knowledge about N-protected Tetrazole?
yanch@ifm.liu.se __________________ Date: Sat, 8 Apr 2000 16:48:31 +0800 From: Jiang Heng Yüklə 2,96 Mb. Dostları ilə paylaş:
|