
	Where results make sense

Topic: Lewis acid

Related Topics

Lewis base

Iron(III) chloride

Electrophile

Boron trifluoride

Coordinate covalent bond

Aluminium chloride

Chloride

Electrophilic substitution

Copper(I) chloride

Aluminum chloride

Copper(II) chloride

Nucleophile

Magnesium chloride

Zinc chloride

Trigonal planar

In the News (Wed 11 Nov 09)

Northern Trust

Marvin Harrison

Peter Chernin

Gary Locke

Match Play

Penelope Cruz

Mickey Rourke

AR Rahman

Danny Boyle

Hugh Jackman

	Acid - Wikipedia, the free encyclopedia
		The acidity constant (or acid dissociation constant) is the equilibrium constant for the reaction of AH with water:
		Later on, BrÃ¸nsted and Lowry defined an acid to be a proton donor and a base to be a proton acceptor.
		Lewis theory defines a " Lewis acid " as an electron-pair acceptor and a " Lewis base " as an electron-pair donor.
	en.wikipedia.org /wiki/Acid (1312 words)

	Lewis acid - Wikipedia, the free encyclopedia
		The Lewis acid and Lewis base theory is one of several Acid-base reaction theories.
		The term acid is ambiguous; this is one of the possible interpretations.
		Unlike traditional acids a Lewis acid does not require a hydrogen ion as the electrophile; rather, another molecule takes up that role.
	en.wikipedia.org /wiki/Lewis_acid (156 words)

	Acid (Site not responding. Last check: 2007-11-06)
		An acid (represented by the generic formula AH) is typically a water-soluble, sour-tasting chemical compound.
		Later on, Bronsted and Lowry defined an acid to be a proton donor and a base to be a proton acceptor.
		A Lewis acid is an electron acceptor, while a Lewis base is an electron donor.
	www.sciencedaily.com /encyclopedia/acid (575 words)

	reviews Lewis Acid/Base Reaction Chemistry
		He begins with the premise that Lewis acids, bases and acid/base complexes are ubiquitous, occurring throughout inorganic, organic and organometallic chemistry.
		Lewis acids and bases are classified by their frontier molecular orbital topology and are placed in a grid, such that 24 different types of bonding interaction can be immediately recognised.
		The four types of Lewis base and six types of Lewis acid are defined and the ways in which these can combine to form 24 types of acid-base complex are demonstrated one by one.
	www.meta-synthesis.com /reviews.html (4694 words)

	Lewis Concept
		Lewis focused his thoughts about acids and bases on what happens when a base accepts a proton and what structiral features of the base allow it to accept a proton.
		Once you say that an acid is an electron pair acceptor, then you're not limited to the idea that an acid has to be a hydrogen ion or some chemical that contains or releases hydrogen ions.
		One commonly cited example of a Lewis acid that does not contain hydrogen is boron trifluoride, shown here accepting a pair of electrons from ammonia.
	dl.clackamas.cc.or.us /ch105-04/lewis.htm (341 words)

	Patent 5321117: Macrocyclic polyester oligomer preparation with Lewis acid as catalyst (Site not responding. Last check: 2007-11-06)
		Macrocyclic poly(alkylene dicarboxylate) oligomers are prepared by the reaction of a dicarboxylic acid chloride such as terephthaloyl chloride with at least one bis(hydroxyalkyl) ester such as bis(4-hydroxybutyl) terephthalate, in the presence of a Lewis acid as catalyst.
		Illustrative Lewis acids are ferric chloride, zinc chloride, zinc bromide, stannous bromide and antimony pentachloride.
		While the use of any Lewis acid may be appropriate, metal halides are especially appropriate and those specifically contemplated in accordance with the present invention are ferric chloride, zinc chloride, zinc bromide, stannous bromide and antimony pentachloride.
	www.freepatentsonline.com /5321117.html (1792 words)

	ChemTeam: The Lewis Theory of Acids and Bases (Site not responding. Last check: 2007-11-06)
		Keep in mind that Bronsted-Lowry, which defines an acid as a proton donor and a base as a proton acceptor, REQUIRES the presence of a solvent, specifically a protic solvent, of which water is the usual example.
		The Lewis definitions of acid and base do not have the constraints that the Bronsted-Lowry theory does and, as we shall see, many more reactions were seen to be acid base in nature using the Lewis definition than when using the Bronsted-Lowry definitions.
		A "Lewis acid" is any atom, ion, or molecule which can accept electrons and a "Lewis base" is any atom, ion, or molecule capable of donating electrons.
	dbhs.wvusd.k12.ca.us /webdocs/AcidBase/Intro-to-Lewis-AcidBase.html (535 words)

	Lewis Concept of Acids and Bases (Site not responding. Last check: 2007-11-06)
		Lewis developed a theory of acids and bases that is based upon the sharing of electron pairs.
		A Lewis acid is a substance that can accept a pair of electrons from another atom to form a new bond.
		All metal cations are potential Lewis acids because their positive charge will readily attract electron pairs and they all have at least on empty orbital.
	erkki.kennesaw.edu /GCII6/gc00012.htm (305 words)

	Lewis Acid Mediated Cyclisations
		Here, in the absence of a sufficiently nucleophilic anion derived from the Lewis acid, the intermediate allyl cation 7 is trapped intramolecularly by the alkoxide nucleophile.
		G L N Peron, J Kitteringham and J D Kilburn, "Lewis Acid Mediated Cascade Reactions of Silyl-Substituted Methylenecyclopropyl Ketones", Tetrahedron Lett, 2000, 1615-18.
		G L N Peron, J Kitteringham and J D Kilburn, "Lewis Acid Mediated Cyclisation of Methylenecyclopropyl Ketones and Aldehydes", Tetrahedron Lett, 1999, 40, 3045-3048.
	www.soton.ac.uk /~jdk1/lewis_acids.htm (294 words)

	Defintion of lewis_acids_and_bases - Chemistry Dictionary (Site not responding. Last check: 2007-11-06)
		Acids are species that donate a proton (H+).
		NH4+ is the conjugate acid of the base NH3, and OH- is the conjugate base of the acid H2O.
		The Lewis definition encompasses the Bronsted-Lowry definition: In the reaction of H+ and OH-, H+ is a Lewis acid because it accepts an electron pair from the OH-.
	www.chemicool.com /definition/lewis_acids_and_bases.html (259 words)

	Chemistry Posters Online - Catalytic Preparation of Aziridines by Asymmetric Fe Lewis Acid (Site not responding. Last check: 2007-11-06)
		An asymmetric Lewis Acid that is effective at catalyzing a wide range of reactions with a high level and predictable sense of enantioselectivity remains to be discovered.
		Yields of aziridine from the iron Lewis acid catalyzed reaction of aryl imines with ethyl diazoacetate.
		Yields of aziridine from the iron Lewis acid catalyzed reaction of aryl imines with phenyl diazomethane.
	alchemy.chem.uwm.edu /research/hossain/posters/mayer1/asyfelewis.html (820 words)

	Ionic Equilibria (Site not responding. Last check: 2007-11-06)
		However the acid HCl does transfer a proton to the base ammonia, NH, to form the ammonium ion, NH, in the solid salt, NH Cl. Thus this is an acid/base reaction by the Brønsted-Lowry definition.
		Lewis noted that some compounds that were not acids or bases under the Bronsted-Lowry definition nevertheless reacted in similar ways as Bronsted-Lowry acids and bases.
		Lewis noted that in all these reactions something was converting an unshared pair of electrons into a bond.
	v.d.singleton.home.att.net /genchem/ionequil.htm (3379 words)

	Lewis (Site not responding. Last check: 2007-11-06)
		The description of an acid and a base by Lewis is consistent with the description by Arrhenius, and with the definition by Bronstead-Lowry.
		The Fe ion is acting as a Lewis acid.
		The CO is acting as a Lewis acid - it can accept a pair of electrons because the multiple bonds means there is a deficiency of valence electrons around the carbon.
	wine1.sb.fsu.edu /chm1046/notes/AcidBase/Lewis/Lewis.htm (523 words)

	The Lewis Acid/Base Interaction Matrix
		When the schematic Lewis acid/base interaction matrix icons are replaced with real chemical species the nature and usefulness of the Lewis acid/base interaction matrix become apparent.
		In the 1960s, Ralph Pearson suggested that Lewis acids and Lewis bases should be classified as hard, borderline or soft, with the observation that: " Hard [Lewis] acids prefer to complex with hard [Lewis] bases and soft [Lewis] acids with soft [Lewis] bases ", the HSAB principle (go here and here for more information).
		Lewis acid and Lewis base types which are rich in congeneric arrays interact to give complex types which are rich in arrays.
	www.meta-synthesis.com /webbook/13_lab-matrix/LAB_matrix.html (890 words)

	Lewis Acid-Base Experiment (Site not responding. Last check: 2007-11-06)
		Lewis acids, which are electron pair acceptors, and Lewis bases, which are electron pair donors, react to form adducts in which a coordinate covalent bond is formed.
		The strength of the interaction between a Lewis acid and a Lewis base is controlled by at least two factors, electronic and steric ( 1).
		Trimethylamine, N(CH, is a Lewis base and because of the electron donating methyl groups, it should be a stronger base than NH when both are compared with a common Lewis acid.
	www.molecules.org /experiments/Coskran/Coskran.html (963 words)

	The Lewis Definitions of Acids and Bases (Site not responding. Last check: 2007-11-06)
		In the Lewis theory of acid-base reactions, bases donate pairs of electrons and acids accept pairs of electrons.
		The Lewis theory suggests that acids react with bases to share a pair of electrons, with no change in the oxidation numbers of any atoms.
		The principal advantage of the Lewis theory is the way it expands the number of acids and therefore the number of acid-base reactions.
	chemed.chem.purdue.edu /genchem/topicreview/bp/ch11/lewis.html (664 words)

	The Yamamoto Group - The University of Chicago
		An excellent candidate as a proton substitute in man-made organic reactions is a Lewis acid.
		After survey of pyrrolidine-based Brønsted acid catalyst, tetrazole catalyst was found to be optimal in synthesis of aminooxy carbonyl compounds in high yields with complete enantioselectivity not only for aldehydes but also for ketones.
		Oxazaborolidine-derived Lewis Acid Assisted Chiral Lewis Acid as a Moisture Tolerant Enantioselective Diels-Alder Catalyst, K. Futatsugi, and H. Yamamoto, Angew.
	yamamotogroup.uchicago.edu /main.html (950 words)

	Three theories of Acids and Alkalis: Arrhenius, Lowry-Bronsted and Lewis. Loreto, Coleraine.
		Each substance in the acid column is converted to its partner in the base column by the removal of a proton.
		A LEWIS ACID IS A SUBSTANCE THAT IS AN ELECTRON-PAIR ACCEPTOR
		The Lewis definition is useful because it allows us to classify so many substances as acids or bases, and because it provides an understanding of the details of many chemical reactions.
	www.lcc.ukf.net /Chem14/acidalkali.htm (1002 words)

	Search Results for Lewis acid - Encyclopædia Britannica
		Much less information is available about Lewis acid –base equilibria than about ordinary acid –base equilibria, but it is clear that the situation is less simple for the former than for the latter.
		In the reaction of a Lewis acid with a base the essential process is the formation of an adduct in which the two species are joined by a covalent bond; proton transfers are not normally involved.
		Acid s (including Lewis acid s) and bases act as powerful catalysts for a great variety of chemical reactions, in the laboratory, in industry, and in processes occurring in nature.
	www.britannica.com /search?query=Lewis+acid (580 words)

	Patent 5030785: Process for preparing long chain alkyl aromatic compounds employing Lewis acid-promoted zeolite ... (Site not responding. Last check: 2007-11-06)
		A Lewis acid is generally considered to be a molecule which is capable of combining with another molecule or ion by forming a covalent chemical bond with two electrons from the second molecule or ion, which is to say, a Lewis acid is an electron acceptor.
		BF.sub.3 is a preferred Lewis acid for use in the alkylation process of this invention.
		Boric acid, 2.59 parts, was added to a solution containing 1 part of 45% KOH solution and 42.96 parts H.sub.2 O. To this was added 8.56 parts of Ultrasil silica, and the mixture was thoroughly homogenized.
	www.freepatentsonline.com /5030785.html (7145 words)

	The Lewis Acid (Site not responding. Last check: 2007-11-06)
		This definition is more general than those we have seen to this point; any Arrhenius acid or base, or any Brønsted-Lowry acid or base can also be viewed as a Lewis acid or base.
		The hydroxide ion donates a pair of electrons for covalent bond formation, thus OH is a Lewis base in this reaction.
		The BF is the Lewis acid and the N(CH is the Lewis base.
	faculty.ssu.edu /~dfrieck/212/rev/acidbase/lewis.htm (224 words)

	MSN Encarta - Search Results - Lewis acid
		Lewis, Gilbert Newton (1875-1946), American chemist best known for his theory of electron sharing in covalent bonds.
		Lewis, Gilbert Newton: theories regarding acids and bases
		Lewis, (Harry) Sinclair (1885-1951), American novelist, whose naturalistic style and choice of subject matter was much imitated by later writers.
	encarta.msn.com /Lewis_acid.html (189 words)

	Outcomes Review Chapter 6 (Site not responding. Last check: 2007-11-06)
		In Lewis acid-base reactions, a nonbonding electron pair on a Lewis base is attracted to a positive center on a Lewis acid and the electrons form a new covalent bond between the two reactants.
		Lewis acid-base reactions also occur between ligands, Lewis bases, and metal ions, Lewis acids, to which the bases bond to form metal ion complexes, many of which are important in biological systems.
		Finally Lewis acid-base reactions occur between nucleophiles, Lewis bases, and electrophiles, Lewis acids, to form a variety of final products from the rearrangements that occur after the initial bond formation.
	www.acs.org /portal/a/c/s/1/acsdisplay.html?DOC=\education\curriculum\genchem_chapt6.html (674 words)

	Lewis Acid/Base Reaction Chemistry
		Within Lewis octet theory, a Lewis base was originally described as a species with an available (reactive) pair of electrons and a Lewis acid as an electron pair acceptor species.
		In the 1960s Klopman updated this idea and suggested that a Lewis base is a species which reacts via its highest occupied molecular orbital or HOMO, and a Lewis acid is a species which reacts via its lowest unoccupied molecular orbital or LUMO, here.
		The six types of Lewis acid and four types of Lewis base can be arranged into an interaction matrix which generates 24 types of Lewis acid/base interaction complex and associated reaction chemistry.
	www.meta-synthesis.com /webbook/12_lab/lab.html (581 words)

	Prof. Yamamoto - Chemistry Department - University of Chicago
		Through his dedicated efforts, Lewis acid of organoaluminum, organoboron, and organotitanium compounds are now recognized as major tools in the synthesis of both simple and complex organic molecules.
		It was his Bronstead acid-Lewis acid combined system, however, which gave him a unique opportunity for the most efficient asymmetric Lewis acid catalyst for Diels Alder reaction.
		His discovery of tartaric acid based catalyst (CAB catalyst) and amino acid based catalyst led to remarkable enantioselective Diels-Alder reaction of a wide range of dienes and dienophiles.
	chemistry.uchicago.edu /fac/yamamoto.shtml (1625 words)

	Theories of acids and bases
		In the sodium hydroxide case, hydrogen ions from the acid are reacting with hydroxide ions from the sodium hydroxide - in line with the Arrhenius theory.
		An acid is a proton (hydrogen ion) donor.
		On the Lewis theory, any reaction in which the ammonia or water used their lone pairs of electrons to form a co-ordinate bond would be counted as them acting as a base.
	www.chemguide.co.uk /physical/acidbaseeqia/theories.html (1946 words)

	Lewis acids and bases
		The most general definition of acids and bases, which encompasses the Arrhenius and Bronsted-Lowry definitions is due to our old friend, Lewis and his dot structures.
		A Lewis acid is defined to be any species that accepts lone pair electrons.
		In fact octet deficient molecules are often strong Lewis acids because they can achieve an octet configuration by accepting a lone pair from a Lewis base.
	www.nyu.edu /classes/tuckerman/honors.chem/lectures/lecture_21/node4.html (216 words)

	The glossary (Site not responding. Last check: 2007-11-06)
		Lewis structures use dots to represent individual electrons and lines to represent covalent bonds.
		The relatively small polynucleotide that carries amino acids and recognizes the codon on mRNA that specifies the amino acid to be incorporated at a particular point on a protein chain.
		An acid for which the acid-dissociation equilibrium constant is significantly smaller than one.
	www.wantwit.com /Chem/glossary2.html (10536 words)

	Acid - Base -LEWIS CONCEPT OF ACID-ARRHENIUS CONCEPT OF BASE-LOWRY AND BRONSTED (Site not responding. Last check: 2007-11-06)
		According to Arrhenius, an acid is a substance, which provides H+ ions in aqueous solution.
		+ Cl According to Lowry and Bronsted concept, an acid is a compound or species which donates or tends to donate a proton.
		According to Lewis concept, "an acid is a compound or species that accepts a pair of electrons."
	www.geocities.com /khawarahmed2002/fourthone.htm (176 words)

Try your search on: Qwika (all wikis)