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Topic: Benzoin condensation

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	Benzoin Condensation
		The Benzoin Condensation is a coupling reaction between two aldehydes that allows the preparation of α-hydroxyketones.
		A second equivalent of aldehyde reacts with this carbanion; elimination of the catalyst regenerates the carbonyl compound at the end of the reaction:
		An Efficient Nucleophilic Carbene Catalyst for the Asymmetric Benzoin Condensation
	www.organic-chemistry.org /namedreactions/benzoin-condensation.shtm (140 words)

	Condensation reaction Summary
		A condensation reaction (also known as a dehydration reaction or dehydration synthesis when water is lost) is a chemical reaction in which two molecules or moieties react and become covalently bonded to one another by the concurrent loss of a small molecule, often water, methanol, or a type of hydrogen halide such as HCl.
		Other condensations, such as the acyloin condensation are triggered by radical or single electron transfer conditions.
		Other organic condensation reactions are Aldol condensations, self-condensation, the acyloin condensation and the benzoin condensation.
	www.bookrags.com /Condensation_reaction (1128 words)

	Medscape MEDLINE search: Benzoin
		Comparative studies on the enantioseparations of racemic hydrobenzoin, together with benzoin and benzoin methyl ether, in capillary zone electrophoresis using sulfated beta-cyclodextrin (S-beta-CD) as a chiral selector in the presence and absence of borate complexation were investigated.
		Characterization of the chemical composition of a byproduct from siam benzoin gum.
		The mixture of bark and gum obtained after size-grading of Siam benzoin gum was studied to establish its potential application as a valuable new grade of the balsamic resin.
	search.medscape.com /uslclient/searchMedline.do?queryText=Benzoin (1173 words)

	Benzoin-bonded organopolysiloxanes and method for the preparation thereof - Patent 4273907
		The invention provides a novel class of organopolysiloxane compounds having at least one benzoin group represented by the general formula ##STR1## in which Ph is a phenyl group and R is a hydrogen atom or an alkyl group, bonded to the silicon atom in a molecule.
		A benzoin-bonded organopolysiloxane represented by the general formula ##STR28## where Q is a benzoin group represented by the general formula ##STR29## Ph is a phenyl group, R is a hydrogen atom or an alkyl group having from 1 to 4 carbon atoms, b is a positive integer and C is 0 or a positive integer.
		The condensation reaction is performed in a solution with an organic solvent such as benzene, toluene and xylene in the presence of a reaction promotor or a condensation catalyst.
	www.freepatentsonline.com /4273907.html (2004 words)

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		As a result, it was confirmed that the substance yielded from the condensation was benzoin.
		The percent recovery of the benzoin was at 67.00% and the percent yield was at 44.79%.
		Benzoin is formed from the condensation of benzaldehyde.
	www.u.arizona.edu /~keslar/academia/chemistry/tetra.doc (1073 words)

	Crystallization is used to purify a solid. The objective is to find a solvent which dissolves the solid (solute) when ...
		The reaction is known as a benzoin condensation ("condensation" because two molecules become condensed to one molecule).
		After cooling, the recrystallized benzoin should be filtered, washed with a minimum of a cold 2:1 mixture of water and 95% ethanol, and air dried for 15 min or left until the next lab period.
		Attach a reflux condenser and heat the mixture on a steam bath, water bath or sand bath until the solids dissolve.
	www.umsl.edu /~orglab/experiments/MULTISTP.html (1942 words)

	Preparation of Hexaphenylbenzene (Site not responding. Last check: 2007-10-30)
		The benzoin condensation was originally discovered by using cyanide ion as a catalyst.
		The benzoin condensation is one of the most important reactions of biochemistry, it is the central reaction in sugar biosynthesis and metabolism.
		In the fume hood heat a mixture of 4 grams of benzoin and 14 mL of concentrated nitric acid for eleven minutes in a beaker of boiling water.
	www.pittstate.edu /chem/courses/chem326/hexaphenyl.html (1534 words)

	ald6q.html (Site not responding. Last check: 2007-10-30)
		The reaction is known historically as the benzoin condensation.
		[Purist would rather not call this process a condensation because it is a dimerization of benzaldehyde without the loss of some small molecule such as water.
		It is this compound that Mitscherlich (1834) oxidized to benzoic acid, which was subsequently decarboxylated to form benzene.
	classes.yale.edu /02-03/chem220a/studyaids/orgo/aldehydes/ald6a.html (72 words)

	Image formation process - Patent 4368253
		The polyester-forming reaction between the dihydric phenol or dihydric alcohol and the diacid or ester-forming derivative thereof is preferably carried out in solution in an organic solvent using a conventional catalyst such as a tertiary amine, or, when the ester-forming derivative is a lower alkyl ester, in the presence of a transesterification catalyst.
		The reactants are used in amounts such that a polyester having from 1 to 200, preferably from 3 to 100, benzoin units is obtained.
		Compounds of formula II where m and p each denote 1, R.sup.1 denotes one of the specified organic groups and R.sup.2 denotes a hydrogen atom may be prepared by reacting a dihydroxybenzoin, prepared as described above, with an alcohol R.sup.1 OH in the presence of an acid catalyst such as toluene-4-sulphonic acid.
	www.freepatentsonline.com /4368253.html (7078 words)

	JCE 2004 (81) 1020 [Jul] Benzoin Condensation: Monitoring a Chemical Reaction by High-Pressure Liquid Chromatography
		JCE 2004 (81) 1020 [Jul] Benzoin Condensation: Monitoring a Chemical Reaction by High-Pressure Liquid Chromatography
		High-pressure liquid chromatography was successfully introduced in the undergraduate advanced organic chemistry laboratory to reinvestigate the cyanide-catalyzed condensation of benzaldehyde to benzoin.
		In addition to an increase in overall yield and purity of the product over the existing procedure the experiment provided the students with a practical hands-on introduction to modern HPLC and its application in process optimization.
	jchemed.chem.wisc.edu /journal/issues/2004/Jul/abs1020.html (235 words)

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		Obtain the mp of the recrystallized benzoin (lit mp listed as 133 and 137 oC for d,l-benzoin, most students will see a mp of 133 oC).
		When you are satisfied that you have the product you want, you may dispose of the first filtrate by neutralizing with dilute HCl, then flushing the aqueous layer down the drain with plenty of water.
		If your instructor requests, run a tlc of the recrystallized product with known samples of benzoin and benzil for comparison of Rf values.
	www.umsl.edu /~orglab/wordfiles/MULTISTP.DOC (2080 words)

	ORGANIC CHEMISTRY II
		For the week of April 19 we will be working up the product from the benzoin condensation.
		A thioester enolate ion condenses with a ketone in the citric acid cycle to produce a carbon-carbon bond
		Esters undergo the Claisen condensation in a manner similar to the aldol reaction
	www.muhlenberg.edu /depts/chemistry/chem202woh/finalexam.htm (973 words)

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		It is a good nucleophile, it stabilizes the intermediate carbanion, and it is a good leaving group.
		3) Various derivatives of benzaldehyde have undergone the benzoin condensation reaction with mixed results.
		Theoretically it should stay in the solvent (the product solidifies out of the mixture).
	www.gpc.edu /~lstrange/2642lab/prelabquestions/answers/benzoin.doc (210 words)

	IngentaConnect Microwave assisted benzoin condensation using thiamine as catalys... (Site not responding. Last check: 2007-10-30)
		IngentaConnect Microwave assisted benzoin condensation using thiamine as catalys...
		Microwave assisted benzoin condensation using thiamine as catalyst
		α-Hydroxyketones were prepared in appreciable yields at a very high speed, (by the benzoin condensation) under microwave irradiation using a catalytic amount of thiamine hydrochloride, from various aromatic as well as heteroaromatic aldehydes.
	www.ingentaconnect.com /content/stl/jcr/2006/00002006/00000004/art00020 (133 words)

	Amazon.com: "benzoin condensation": Key Phrase page (Site not responding. Last check: 2007-10-30)
		See all pages with references to benzoin condensation.
		Another example is the benzoin condensation which in organic chemistry is cata- lyzed by cyanide ion.
		123,124 Thiazolium salts catalyse the benzoin condensation 125 by a mechanism involving the thiazolium C-2 anion.126,127 Thiazolium-functionalized -cyclodextrin can bind a benzaldehyde molecule, and catalyse reactions like...
	www.amazon.com /phrase/benzoin-condensation (500 words)

	Help about benzoin condensation
		I am planning to do one new instance of benzoin condensation, with pyridine-4-carboxaldehyde as the carbonyl compound to receive, 2-hydroxy-1,2-dipyridin-4-ylethanone, the resultant benzoin compound.
		However I have some doubts as suggested in this website, since pyridine nitrogen is a good mesomeric effect provider; this is told to make the reactions harder.
		, pyridine aldehyde-derived benzoin derivatives, are present, so you are right, Movies, about the decreased reactivity of benzene ring.
	www.physicsforums.com /showthread.php?p=337556 (755 words)

	Meeting 2 Chem 30BL (Elimination)
		Referring to the benzoin condensation, answer the following questions.
		How many grams of benzoin are isolated if the reaction runs in 80% yield?
		Draw a sketch for the setup used for the filtration of the benzoin and label all parts needed.
	www.chem.ucla.edu /~bacher/General/30BL/problems/week2Su05.html (346 words)

	Benzoin condensation - Wikipedia, the free encyclopedia
		In one study a custom designed N-Heterocyclic Carbene (NHC, the framework is related to thiazolium salts) was found to be able to bring about an enantioselective intramolecular benzoin condensation (scheme 2)
		^ Benzoin Roger Adams and C. Marvel Organic Syntheses, Coll.
		This page was last modified 05:42, 31 July 2006.
	en.wikipedia.org /wiki/Benzoin_condensation (456 words)

	Help about benzoin condensation Text - Physics Forums Library
		View Full Version : Help about benzoin condensation
		I've searched Chemical Abstracts in the period 2004-1998, and found that all kinds of pyridoins, i.e., pyridine aldehyde-derived benzoin derivatives, are present, so you are right, Movies, about the decreased reactivity of benzene ring.
		Also note that the lone pairs of the nitrogen in pyridine do not contribute to delocalization.
	www.physicsforums.com /archive/index.php/t-46820.html (707 words)

	ORGANIC CHEMISTRY II
		Project 12.1: Thiamine-Catalyzed Benzoin Condensation - set up reaction
		Polyesters are made by condensation rather than addition
		A nitrile is a carboxylic acid derivative that lacks a carbonyl group
	www.muhlenberg.edu /depts/chemistry/chem202woh/exam3.htm (568 words)

	[No title]
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		Each rotates in its own direction, but the overall effect is cancelled out What functions does the cyano anion perform as the catalyst in the Benzoin Condensation?
		it is a good nucleophile it stabilizes the intermediate carbanion it is a good leaving group all of the above Why wouldn’t p-cyanobenzaldehyde undergo the benzoin condensation?
	www.gpc.edu /~lstrange/2642lab/prelabquiz/benzoin.doc (134 words)

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