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Topic: Enolate anion

Related Topics

Aldol condensation

Enol

Carbonyl group

Cannizaro reaction

Base (chemistry)

Polyoxymethylene

Virusoid

Electrophilic addition

Oxidation

Formic acid

Garut

Layoff

Amyl nitrite

Formaldehyde

VU meter

	Aldol reaction - Wikipedia, the free encyclopedia
		The enol or enolate is itself generated from a carbonyl compound, often an aldehyde or ketone, using acid or base.
		In general, kinetic enolates are favored by cold temperatures, relatively ionic metal-oxygen bonds, and rapid deprotonation using a slight excess of a strong, hindered base while thermodynamic enolates are favored by higher temperatures, relatively covalent metal-oxygen bonds, and longer equilibration times for deprotonation using a slight sub-stoichiometric amount of strong base.
		In the case of an E enolate, the dominant control element is allylic 1,3-strain whereas in the case of a Z enolate, the dominant control element is the avoidance of 1,3-diaxial interactions.
	en.wikipedia.org /wiki/Aldol_reaction (2310 words)

	Enolate anion - Wikipedia, the free encyclopedia
		An enolate anion is an anion derived by loss of a proton from the alpha carbon of a carbonyl group; it is the anion of an enol.
		For instance, a base abstracts one proton from acetone to form enolate anion.
		The enolate anion is stabilized by resonance and therefore the alpha hydrogen is acidic.
	en.wikipedia.org /wiki/Enolate_anion (95 words)

	Chemical Reactivity
		For example, aldehyde enolate bases are likely to undergo the aldol reaction during their formation, and ketones like 2-heptanone have two different alpha-carbons, each capable of enolization.
		The ambident nature of enolate anions also enables electrophilic attack at both oxygen and carbon, but in most synthesis applications bonding to carbon is desired.
		Finally, enolate anions may often be formed as E/Z stereoisomers, and it has been shown that reaction stereoselectivity, when new chiral centers are created, depends on the enolate configuration.
	www.cem.msu.edu /~reusch/VirtualText/special3.htm (9077 words)

	[No title]
		The second set of reactions hydrolyzes the ester groups, protonates the resulting carboxylate anions, and causes one carboxylate group to be eliminated as CO This is a mixed aldol condensation.
		The nucleophilic enolate anion is formed on the alpha C of cyclohexanone attacks the electrophilic carbonyl C of benzaldehyde.
		The enolate nucleophile formed at the alpha C of cyclopentanone attacks the carbonyl C of the ester.
	www.du.edu /~jhornbac/organic/oldexams/f98-1/q3pe1ans1.html (398 words)

	Carbonyl Reactivity
		Since the negative charge of an enolate anion is delocalized over the alpha-carbon and the oxygen, as shown earlier, electrophiles may bond to either atom.
		For alkylation reactions of enolate anions to be useful, these intermediates must be generated in high concentration in the absence of other strong nucleophiles and bases.
		A full analysis of the factors that direct substitution of enolate anions to carbon or oxygen is beyond the scope of this text.
	www.cem.msu.edu /~reusch/VirtualText/aldket2.htm (3411 words)

	Lecture 26 - The Birch Reduction
		The anion is protonated by the solvent (ammonia) and the radical is then further reduced (addition of the second electron) to generate a new anion.
		Pathway 2 is the favored one, since this does not place the anion on a center that is already electron rich (remember, we can use resonance structures to figure out what centers are more electron-rich and which centers not less electron rich).
		The pKa of this enolate anion is to low to deprotonate ammonia (roughly 25 for the enolate versus >35 for ammonia).
	www.chem.binghamton.edu /HANDY/chem231/lect2627/lect26.htm (405 words)

	LDA
		The extent to which an enolate anion forms depends on the strength of the base used to deprotonate the ketone.
		Thermodynamic enolate is formed under reaction conditions that favor equilibration between initially formed kinetic enolate (kinetic enolate is always formed first, product of the faster reaction of the two) and the original ketone.
		Before we discuss the alkylation reactions of enolates, we must first define what an ambident nucleophile is. An enolate anion is a an ambident nucleophile because it can react with an electrophile either as an alkoxide anion or as a carbanion.
	www.wiu.edu /users/mftkv/Chem332/LDA.html (659 words)

	[No title]
		After the enolate ion has been formed, it is a reactive, negatively charged compound and, thus, can behave as a nucleophile or a base.
		If the enolate anion behaves as a nucleophile instead of behaving as a base and being protonated, then the enolate anion can add to the carbonyl carbon of another molecule.
		If only one type of carbonyl compound is present, then half of the material will be used to generate the enolate anion and the other half will be used as the carbonyl carbon that is attacked by the nucleophile (the enolate anion).
	www.chem.wisc.edu /~newtrad/CurrRef/AIDStopic/AIDS.AldKetRxns.html (2217 words)

	Chem 3020
		deprotonation ® resonance stabilized enolate anion ® protonation
		The enolate anion is the conjugate base of
		An enolate anion from a b-dicarbonyl compound serves as a nucleophile
	science.csustan.edu /cstessman/3020/ch22.htm (1225 words)

	CHEM 3312: General Organic Chemistry - Homework 4
		Draw any enolate anions (and their resonance structure) that could form if the cinerin structure above were treated with a base (such as NaOH).
		The enolate anion of the ester group in cinerin is significantly harder to form than the other three you drew.
		One of the three enolate anions that can form around the ketone in cinerin is more easily formed than the other two.
	www.chem.memphis.edu /parrill/chem3312/Homework4.htm (332 words)

	Strathprints: The University of Strathclyde Institutional Repository - Trapping, Stabilization, and Characterization of ...
		Strathprints: The University of Strathclyde Institutional Repository - Trapping, Stabilization, and Characterization of an Enolate Anion of a 1,6-Adduct of Benzophenone Chelated by a Sodium Alkylamidozincate Cation
		Trapping, Stabilization, and Characterization of an Enolate Anion of a 1,6-Adduct of Benzophenone Chelated by a Sodium Alkylamidozincate Cation
		Hevia, E. and Honeyman, G.W. and Kennedy, A.R. and Mulvey, R.E. Trapping, Stabilization, and Characterization of an Enolate Anion of a 1,6-Adduct of Benzophenone Chelated by a Sodium Alkylamidozincate Cation.
	eprints.cdlr.strath.ac.uk /750 (303 words)

	Enolates
		In Chapter 18 we introduced the enolates of aldehydes and ketones (review) and looked at their reactions as C nucleophiles (review).
		When preparing ester enolates, the base is normally chosen to match the alcohol portion of the ester...
		Hence, the anion of a ketone where there are extra alkyl groups is less stable than that of an aldehyde, and so, a ketone is less acidic.
	www.mhhe.com /physsci/chemistry/carey/student/olc/ch21enolates.html (620 words)

	[No title] (Site not responding. Last check: 2007-11-01)
		Enolate anions can undergo nucleophilic addition to carbonyl groups.
		In aldol condensations, an enolate anion undergoes nucleophilic addition to a ketone or aldehyde producing a
		Enolate anions of esters can undergo nucleophilic addition to the carbonyl group of another ester.
	people.uis.edu /gtram1/organic/a-substitution/aldol.htm (216 words)

	[No title]
		You need to use the cyclic amine shown, and read slide 6 to see the enolate explination (basically, there is steric interference which makes the kinetic enolate more stable because it does not have the steric interference that the thermodynamic enolate does).
		Basically, it’s an enolization reaction in which the enolate anion forms, but then the only other thing that’s in the mixture for it to react with is another carbonyl compound.
		So the enolate anion will “attack” the carbonyl carbon, which will give up its double bond with the oxygen.
	www.gpc.edu /~lstrange/2642smart/fa03/november11th.doc (563 words)

	John A. Gerlt
		-proton of a carboxylate anion, we have predicted the functions of unknown proteins discovered in genome projects.
		We are using directed evolution to explore the functional restrictions available to members of this superfamily, aiming to obtain novel catalysts for new reactions.
		In contrast to the enolase superfamily, the positions of the essential functional groups in this superfamily cannot be restricted to known positions within the structure.
	www.scs.uiuc.edu /chem/gerlt.html (602 words)

	Fundamental practicum: A naphthalene cyclophane as a selective enolate anion receptor (Site not responding. Last check: 2007-11-01)
		The encapsulation of anions is best achieved by employing receptors endowed with cationic binding sites.
		Enolization catalysts and enolate-binding synthetic hosts have the potential for controlling the regiochemistry, stereochemistry, and the reactivity of reactions involving enolates.
		This paper describes synthetic efforts towards the preparation of a naphthalene cyclophane designed as a selective anion receptor.
	epublish.utdallas.edu /dissertations/AAI9409849 (338 words)

	Chem 3020
		Overall, an enolate is added to the green carbonyl which becomes an alcohol
		the enolate anion of one aldehyde or ketone molecule
		If LDA is used to form the enolate anion, the conversion to enolate is complete
	science.csustan.edu /almy/3020/ch23.htm (1535 words)

	Practice Final Exam
		4.(contd.) (b) (15 points) The preparation of 4g involves the enolate of an amide. Draw all three resonance forms of this enolate.
		(c) (10 points) The preparation of 8a involves the anion of a nitrile (2-methylpropanenitrile). Draw both resonance forms for this anion.
		[Hint: the nitrile anion is not connected with the reason- a simple enolate anion would react similarly.]
	www2.potsdam.edu /walkerma/342ts03.htm (335 words)

	Chapter 1 - Alkylation of Nucleophilic Carbon
		Position of equilibrium determined by stability of enolate anion.
		Under kinetic conditions the enolate ratio is determined by the relative rates of the 2 competing proton abstraction reactions.
		Normally alkylation goes in the direction of the most substituted enolate which leads to the more substituted product.
	www.chem.uh.edu /Courses/Thummel/Chem6352/Ch01 (329 words)

	[No title]
		Pay particular attention to the regiochemistry and stereochemistry of the reaction.
		An enolizable carbon will lose a proton in the presence of the strong base, such as methoxide anion, to give an equilibrium enolate anion.
		An enolizable carbon will lose a proton in the presence of the strong base, lithium diisopropylamide (LDA) to give an enolate anion.
	www.chem.uic.edu /web1/OCOL3/CH23/23B/23BBANS.HTM (276 words)

	[No title]
		The aldol reaction is one of the most powerful methods available for forming a carbon-carbon bond.
		In principle, either the negatively charged carbon of the carbanion or the negatively charged oxygen of the enolate could act as a nucleophile; a stronger bond forms in this reaction if carbon serves as the nucleophile.
		In this example, a second molecule of acetaldehyde provides the carbonyl group that undergoes nucleophilic attack.
	spot.pcc.edu /~sbrookha/CH243/lab_handouts/Aldol_rev.doc (489 words)

	enolaterexns (Site not responding. Last check: 2007-11-01)
		The enol form of the chiral ketone is achiral and thus the equilibration of the ketone and the enol facilitated by the base (or acid) will result in the loss of optical activity.
		-proton by a base followed by the protonation of the resulting enolate anion by water (aq.
		Equilibration of the enol with the keto form will result in the racemic mixture as shown below.
	www.wiu.edu /users/mftkv/Chem332/enolaterexns.html (113 words)

	Chapter 18 Notes
		reaction of an enolate as nucleophile with a carbonyl group,
		more stable enolate (or enol) is the more substituted (thermodynamically favored)
		more rapidly formed enolate is the less substituted (kinetically favored)
	chem.pdx.edu /~wamserc/C335W00/18notes.htm (441 words)

	Energy Citations Database (ECD) - Energy and Energy-Related Bibliographic Citations
		Energy Citations Database (ECD) Document #6949248 - Stepwise mechanism for gas-phase unimolecular ion decompositions.
		Isotope effects in the fragmentation of tert-butoxide anion
		Availability information may be found in the Availability, Publisher, Research Organization, Resource Relation and/or Author (affiliation information) fields and/or via the "Full-text Availability" link.
	www.osti.gov /energycitations/product.biblio.jsp?osti_id=6949248 (139 words)

	Model of Cyclopentanone Enolate Anion and 2-Ethylcyclopentanone
		By using a very strong base, such as LDA, a good yield of enolate anion can be synthesized, and this can react as a good nucleophile in reactions with, for example, haloalkanes.
		If this enolate (left) is reacted with bromoethane, the alpha-alkylated product (right) can be formed.
		To rotate: press left mouse button on molecule and drag
	wps.prenhall.com /wps/media/objects/725/743350/alkylation1.html (76 words)

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