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Topic: Nucleophilic attack

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Nucleophilic addition

Organic reaction

Organic chemistry

	Nucleophilic Substitution & Elimination
		One outcome of this is that the carbocation intermediate "lives" long enough for a nucleophile to approach it on either face of the molecule.
		The fact that the nucleophile is not involved in the rate determining step of an S
		When the nucleophile is also the solvent, the reaction is called "solvolysis." Solvents like water and alcohols are particularly useful here, because they provide both a nucleophilic pair of electrons on the oxygen atom of the OH group and a fairly polar solvent which helps to stabilize the strongly polar transition state.
	chemistry2.csudh.edu /rpendarvis/SN1Elim.html (2034 words)

	SN1 reaction - LearnThis.Info Enclyclopedia (Site not responding. Last check: )
		Nucleophilic attack: a nucleophile (molecule B) joins onto the carbon.
		If the nucleophile B is a neutral molecule (very often it is a solvent molecule), a third step is required to complete the reaction.
		Nucleophilicity is irrelevant in the determining step's rate, in which only the substrate is crucial.
	encyclopedia.learnthis.info /s/sn/sn1_reaction.html (219 words)

	243may23
		Nucleophilic attack by the carboxylate ion on the gamma phosphorus group with subsequent nucleophilic acyl substitution with a thiol to form the thioester.
		Nucleophilic attack by the carboxylate ion on the Beta phosphorus group with subsequent nucleophilic acyl substitution with a thiol to form the thioester.
		Nucleophilic attack by the carboxylate ion on the alpha phosphorus group with subsequent nucleophilic acyl substitution with a thiol to form the thioester.
	spot.pcc.edu /~chandy/243/243may23.html (478 words)

	Nucleophilic substitution reaction Info - Bored Net - Boredom (Site not responding. Last check: )
		An example of nucleophilic substitution is the hydrolysis of an alkyl bromide, R-Br, under alkaline conditions, where the "attacking" nucleophile is hydroxide ion, OH
		The two main mechanisms of nucleophilic substitution are called SN1 and SN2.
		The rate of the overall reaction is essentially equal to that of carbocation formation, which does not involve the attacking nucleophile.
	www.borednet.com /e/n/encyclopedia/n/nu/nucleophilic_substitution_reaction.html (398 words)

	Uracil in Addressable Protein Targeting
		Nucleophilic attack at the C6 position of the cytosine moiety by a cysteine residue at the active site rapidly produces a resonance-stabilized carbanion that is activated to attack a methyl group present on bound S-Adenosylmethionine co-factor, through C5 of cytosine.
		In this model of the chemical reaction, the break-up of the glutamic acid-arginine salt bridge is stabilized by the capture of a proton poised between the ionized carboxyl oxygen of the glutamic acid and N3 of cytosine.
		The initial nucleophilic attack of uracil by the enzyme is not favored because the resulting intemediate must develop negative charge on O4 as the negatively charged carboxyl group on glutamic acid forms a hydrogen bond with N3.
	www.islandone.org /Foresight/Conferences/MNT05/Papers/Wendel (4086 words)

	Tiffany's Chime
		The nucleophile could approach the substrate from the same side as the leaving group, one group exchanging for the other, which is called frontside displacement.
		Charge: Because nucleophilic attack is characterized by the formation of a bond with an electrophilic carbon center, the more negative the attacking species the faster the reaction should be.
		As the nucleophile approaches the electrophilic carbon, the latter rehybridizes, and the electron pair of the pi bond moves over to the oxygen, thereby producing the characteristic "tetrahedral intermediate, an alkoxide ion.
	www.ucalgary.ca /~rauk/saunders.html (1087 words)

	1970-1979
		Nucleophilic Displacements upon Phenyl Esters in Which the Direct Relationship between Basicity of the Leaving Group and Rate Is Determined by Ground State Conformations.
		Nucleophilic Catalysis of the Aromatization of an Arene Oxide.
		Nucleophilic Displacement on the Arene Oxides of Phenanthrene.
	www.chem.ucsb.edu /~tcb_group/1970.htm (1735 words)

	Nucleophilic substitution - Enpsychlopedia (Site not responding. Last check: )
		In chemistry, nucleophilic substitution is a class of substitution reaction in which a electron-rich nucleophile attacks a molecule and replaces a group or atom, called the leaving group.
		Nucleophilic substitution reactions are commonplace in organic chemistry, and they can be broadly categorised as taking place at an aliphatic (saturated) carbon or at (less often) an aromatic or other unsaturated carbon centre.
		Nucleophilic substitutions can be accompanied by an allylic rearrangement as seen in reactions such as the Ferrier rearrangement.
	www.grohol.com /psypsych/SNX (683 words)

	Curly arrows: nucleophilic reactions
		When the nucleophile is also used as the solvent for the reaction, the substitution reaction is called a solvolysis.
		In protic media with non-basic nucleophiles under neutral or acidic conditions, tertiary substrates can be orders of magnitude more reactive than their primary or secondary counterparts.
		If some of the nucleophiles or electrophiles look unfamiliar, use the chemistry that you know to work out a realistic mechanism and remember, you are looking for a substitution (displacement) reaction overall.
	www.abdn.ac.uk /curly-arrows/org/n1.htm (1178 words)

	Competing Pathways in the Reaction of the Pesticide Fenitrothion (Site not responding. Last check: )
		In all cases, attack at the phosphorus center of the substrate by the nucleophile is in competition with O-Ar bond cleavage, the latter being an S
		The reactions of organophosphorus compounds with various types of nucleophiles have been studied by numerous workers in the field of organophosphorus chemistry and a large body of data is available.
		Attack by ethoxide at the P center is catalyzed by alkali metal ethoxides.
	www.arkat-usa.org /ark/journal/2001/I12_Tee/314/314.asp (2596 words)

	Product Distribution in the Nitration of Toluene (Site not responding. Last check: )
		The electrophilic frontier density is a measure of the susceptibility of the substrate to attack by an electrophile.
		On the other hand, the nucleophilic frontier density is a measure of the susceptibility of the substrate to attack by a nucleophile.
		Nucleophilic susceptibility may be applied to the arenium ions generated from ortho, meta or para attack of toluene by the nitronium ion.
	www.molecules.org /experiments/AndersonS/AndersonS.html (1514 words)

	243april11
		The H+ increases the rate of formation of the tetrahedral intermediate, because the protonation of the carbonyl carbon increases the susceptibility of a nucleophilic attack.
		The carboxylate ion is not attacked by a nucleophile, thus the reaction is not reversible.
		A. After the nucleophilic attack on the carbonyl carbon, an alkoxide ion is formed that can be protonated by the solvent.
	spot.pcc.edu /~chandy/243/243april11.html (414 words)

	Mechanisms of in Situ Activation for DNA-Targeting Antitumor Agents
		The nucleophilic character of 14 was demonstrated by a protonation at C1, with the proton unequivocally derived from solvent,
		Attack of the arylamine on this ketone, followed by elimination of water leads to 19, a mitosene analogous to that formed in the activation cascade of the mitomycins (13).
		In the case of ptaquiloside, attack on the cyclopropane of the activated diene occurs primarily at N3 of adenine as well as N7 of guanine, resulting in unusually facile, room-temperature single-strand cleavage reactions.
	pubs.acs.org /cgi-bin/sample.cgi/chreay/2002/102/i07/html/cr010046q.html (9341 words)

	nucleophilic addition - carbonyl compounds and hydrogen cyanide (Site not responding. Last check: )
		The carbon-oxygen double bond is highly polar, and the slightly positive carbon atom is attacked by the cyanide ion acting as a nucleophile.
		Nucleophiles are either fully negative ions or contain a fairly negative region somewhere in a molecule.
		In the first stage, there is a nucleophilic attack by the cyanide ion on the slightly positive carbon atom.
	www.chemguide.co.uk /mechanisms/nucadd/hcn.html (927 words)

	Additions to Alkenes
		These steps -- first an electrophile attacks the pi bond to form a carbocation, second a nucleophile attacks the carbocation -- are the key steps in the most important reactions of alkenes, electrophilic addition reactions.
		is thus the electrophile and the Br is the nucleophile.
		Something else is happening, something which prevents the nucleophilic bromide ion from attacking the face of the carbocation which already is attached to the first bromine.
	chemistry2.csudh.edu /rpendarvis/AlkeneAddn.html (1583 words)

	Steve's place - Reaction Mechanisms
		Nucleophiles are chemical species that are electron rich (may have lone pairs) and seek out positive charge (nucleus is +).
		The reaction mechanisms of carbonyl compounds are important in biology: the formation of imines in particular is widely found, for example in the isomerisation of the compound retinal, which is responsible for detecting light in the rod cells of the mammalian retina.
		The reaction starts with a simple nucleophilic attack - lone pairs on nitrogen attack carbonyl group, with upshot that electrons are removed from the NH bond in the amine group and form a new bond to the carbon.
	www.steve.gb.com /science/reaction_mechanisms.html (2360 words)

	LECTURE 5
		The p-electrons shield the molecule from nucleophilic attack.
		The phosphorous ylides have hybrid structures, and it is the negative charge on carbon (the carbanion in the ylide) that is responsible for their nucleophilic attack on carbonyl carbon.
		In aldol condensation, nucleophilic attack leads to addition, which is a typical reaction of aldehydes and ketones, whereas in claisen condensation, the nucleophilic attack leads to substitution, which is also the typical reaction of acyl compounds.
	www.uiowa.edu /intlinet/unijos/departments/pharmacology/Afolabi/add.react.htm (1400 words)

	Publicacions Reactivitat
		In the gas phase, the attack of a hydroxyl group on a carbonyl compound may involve an interaction between the hydroxyl ion and a proton, followed by elimination of the proton and formation of a water molecule.
		This reaction may interfere with the nucleophilic attack to the carbonyl group, which is related to the mechanism of enzymatic acylation in lactams.
		Epimerization at H7, a nucleophilic attack of hydroxyl ion on the,
	www.uib.es /depart/dqu/dqf/mallorqui/publicacionsa.htm (4901 words)

	Inetrnet Journal of Science: Canping Pan, Akinori Hirashima et al., Results and Discussions. part3-3 (Site not responding. Last check: )
		The electrophilic, nucleophilic susceptibility, and superdelocalizability investigations make it clear that benzyl ring of OA and N12, O16, and O17 of the chain are suitable for either electrophiles, nucleophiles or radicals.
		Electrophilic and nucleophilic susceptibility are measures of the susceptibility of the substrate to attack by an elctrophile or a nucleophile.
		With high values of Density HOMO means loosely bound electrons which are reactive to electrophilic attack, with high values of Density LUMO means loosely bound electrons which are reactive to nucleophilic attack.
	www.netsci-journal.com /97v1/97013/res-dis3-3.htm (905 words)

	Investigate the chemical properties of alkanals and alkanones.
		When the nucleophile attacks the carbonyl group, it uses its lone pair electrons to form a bond with the carbonyl carbon atom.
		Therefore, the aldehyde molecule is relative open to the attack of nucleophiles.
		In ketones, the two alkyl or aryl substituents at the carbonyl carbon cause a greater steric hindrance to the nucleophiles from approaching the carbonyl carbon atom.
	www.coursework.info /i/51808.html (454 words)

	Nucleophilic substitution reaction: Definition and Links by Encyclopedian.com - All about Nucleophilic substitution ...
		In chemistry, nucleophilic subsitution is a type of chemical reaction in which one nucleophile (electron donor) replaces another.
		S stands for chemical substitution[?], N stands for nucleophilic, and the number represents the order of the reaction.
		rate = k[RX][OH The nucleophile enters on the opposite side of the carbon to the leaving group, so an optically active substrate has its structure inverted.
	www.encyclopedian.com /nu/Nucleophilic-substitution-reaction.html (228 words)

	[No title] (Site not responding. Last check: )
		The three fundamental carbonyl group mechanism steps are: Nucleophilic attack at carbon: Electrophilic attack at oxygen: Note that electrophilic attack at the (bond is the same as electrophilic attack at the oxygen because the products are resonance structures, and therefore the reactions are identical.
		Because resonance is a stabilizing effect, the loss of resonance raises the transition state energy for this nucleophilic attack.
		In order of decreasing reactivity to nucleophilic addition: aldehyde > ketone, because: Carbonyl carbon (+: The charge on an aldehyde carbonyl carbon is greater than on a ketone because an aldehyde bears one electron-donating alkyl group attached to the carbonyl, whereas the ketone has two.
	www.chem.leeds.ac.uk /People/CMR/labstuff/litreviews/carbonylchemistry.doc (868 words)

	Protein Degradation
		During catalysis, there is nucleophilic attack of the hydroxyl oxygen of a serine residue of the protease on the carbonyl carbon of the peptide bond that is to be cleaved.
		During attack of the serine hydroxyl oxygen, a proton is transferred from the serine hydroxyl to the imidazole ring of the histidine, as the adjacent aspartate carboxyl is H-bonded to the histidine.
		Deprotonation of the cysteine sulfhydryl by an adjacent histidine residue is followed by nucleophilic attack of the cysteine S on the peptide carbonyl carbon.
	www.rpi.edu /dept/bcbp/molbiochem/MBWeb/mb2/part1/protease.htm (1940 words)

	Presentation3 (Site not responding. Last check: )
		Nucleophilic attack on the acyl carbon of the bond to be cleaved by the serine 195 —OH and formation of covalent tetrahedral ES complex.
		Nucleophilic attack by water on the acyl intermediate on ser195 and abstraction of a proton from water by His 57 leads to the formation of a second tetrahedral intermediate.
		Collapse of tetrahedral intermediate leading to the cleavage of C-O acyl bond to ser195, reprotonation of Ser195 by His 57 and regeneration of catalytic triad.
	www.arches.uga.edu /~kumarj/bcmb8010/pres3.html (129 words)

	Fats & Soaps
		This is followed by attack of the nucleophilic alpha carbon of the enolate on the carbonyl carbon of a second molecule of the ester.
		That is, attack by nucleophilic carbon atom at the carbonyl carbon of an ester, which is followed by loss of the alcohol portion of the ester as a leaving group.
		The four carbon ester which is thus produced is attacked at its carbonyl carbon by another molecule of the carbon nucleophile and the cycle continues.
	chemistry2.csudh.edu /rpendarvis/ester-fats.html (1715 words)

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