104 USES OF REAGENTS IN ORGANIC CHEMISTRY

The following list summarizes the uses of some important reagents in organic chemistry. The reagents are listed alphabetically, followed by brief descriptions of the uses of each.

Acetic acid, CH3COOH: Reacts with vinylic organoboranes to yield alkenes. The net effect of alkyne hydroboration followed by protonolysis with acetic acid is reduction of the alkyne to a cis alkene.

Acetic anhydride, (CH3CO)2O: Reacts with alcohols to yield acetate esters.

Aluminum chloride, A1C13: Acts as a Lewis acid catalyst in Friedel—Crafts alkylation and acylation reactions of aromatic ring compounds.

Ammonia, NH3: A solvent for the reduction of alkynes by lithium metal to yield trans alkenes. Reacts with acid chlorides to yield amides.

Borane, BH3: Adds to alkenes, giving alkylboranes that can be oxidized with alkaline hydrogen peroxide to yield alcohols . Adds to alkynes, giving vinylic organoboranes that either can be treated with acetic acid to yield cis alkenes or can be oxidized with alkaline hydrogen peroxide to yield aldehydes. Reduces carboxylic acids to yield primary alcohols.

Bromine, Br2: Adds to alkenes yielding 1,2-dibromides. Adds to alkynes yielding either 1,2-dibromoalkenes or 1,1,2,2-tetrabromoalkanes. Reacts with arenes in the presence of ferric bromide catalyst to yield bromoarenes. Reacts with ketones in acetic acid solvent to yield c-bromo ketones. Reacts with carboxylic acids in the presence of phosphorus tribromide to yield obromo carboxylic acids (Hell—Volhard—Zelinskii reaction;. Reacts with methyl ketones in the presence of sodium hydroxide to yield carboxylic acids and bromoform (haloform reaction. Oxidizes aldoses to yield aldonic acids.

N-Bromosuccinnnide (NBS), (CH2CO)2NBr: Reacts with alkenes in the presence of aqueous dimethylsulfoxide to yield bromohydrins. Reacts with alkenes in the presence of light to yield allylic bromides (Wohi—Ziegler reaction. Reacts with alkylbenzenes in the presence of light to yield benzylic bromides.

di-tert-Butoxy dicarbonate, (t-BuOCO)2O: Reacts with amino acids to give t-BOC-protected amino acids suitable for use in peptide synthesis (Section 27.11). Butyllithium, CH3CH2CH2CJJ2Lj: A strong base that reacts with alkynes to yield acetylide anions that can be alkylated. Reacts with dialkylamines to yield lithium dialkylamide bases such as LDA, lithium diisopropylamide.

Carbon dioxide, C02: Reacts with Grignard reagents to yield carboxylic acids. Reacts with phenoxide anions to yield o-hydroxybenzoic acids (Kolbe—Schmitt carboxylation reaction.

Chlorine, Cl2: Adds to alkenes to yield 1,2-dichiorides. Reacts with alkanes in the presence of light to yield chioroalkanes by a radical chain reaction pathway. Reacts with arenes in the presence of ferric chloride catalyst to yield chioroarenes. m-Chloroperoxybenzoic acid, m-C1C6H4CO3H: Reacts with alkenes to yield epoxides. Chromium trioxide, Cr03: Oxidizes alcohols in aqueous sulfuric acid (Jones reagent) to yield carbonyl-containing products. Primary alcohols yield carboxylic acids, and secondary alcohols yield ketones.

Cuprous bromide, CuBr: Reacts with arenediazonium salts to yield bromoarenes (Sandmeyer reaction).

Cuprous chloride, CuC1: Reacts with arenediazonium salts to yield chioroarenes (Sandmeyer reaction).

Cuprous cyanide, CuCN: Reacts with arenediazonium salts to yield substituted benzonitriles (Sandmeyer reaction).

Cuprous iodide, Cul: Reacts with organolithiums to yield lithium diorganocopper

reagents (Gilman reagents).

Diazomethane, CH2N2: Reacts with carboxylic acids to yield methyl esters.

Dicyclohexylcarbodiimide (DCC), C6H11—N=C=N—C₆H₁₁: Couples an amine with a carboxylic acid to yield an amide. DCC is often used in peptide synthesis.

Diethyl acetamidomalonate, CH3CONHCH(CO₂Et)₂: Reacts with alkyl halides in a common method of a-amino acid synthesis.

Diethylaluminum cyanide, (Et)₂AICN: Reacts with α,β-unsaturated ketones to yield β-keto nitriles.

Dihydropyran: Reacts with alcohols in the presence of an acid catalyst to yield tetrahydropyranyl ethers that serve as useful hydroxyl-protecting groups.

Diiodomethane, CH212: Reacts with alkenes in the presence of zinc—copper alloy to yield cyclopropanes (Simmons—Smith reaction).

Diisobutylaluminum hydride (DIBAH), (i-Bu)₂AlH: Reduces esters to yield aldehydes. Reduces nitriles to yield aldehydes.

2,4-Dinitrophenyihydrazine, 2,4-(N0₂)₂C₆H₃NHNH₂: Reacts with ketones and aldehydes to yield 2,4-DNP’s that serve as useful crystalline derivatives.

Disiamylborane, [(CH₃)₂CHCH(CH₃)]₂BH: A hindered dialkylborane that adds to terminal alkynes, giving trialkylboranes that can be oxidized with alkaline hydrogen peroxide to yield aldehydes.

1,2-Ethanedithiol, HSCH₂CH₂SH: Reacts with ketones or aldehydes in the presence of an acid catalyst to yield dithioacetals that can be reduced with Raney nickel to yield alkanes.

Ethylene glycol, HOCH₂CH₂OH: Reacts with ketones or aldehydes in the presence of an acid catalyst to yield acetals that serve as useful carbonyl-protecting groups.

Ferric bromide, FeBr₃: Acts as a catalyst for the reaction of arenes with bromine to yield bromoarenes.

Ferric chloride, FeCl₃: Acts as a catalyst for the reaction of arenes with chlorine to yield chloroarenes.

Grignard reagent, RMgX: Adds to carbonyl-containing compounds (ketones, aldehydes, esters) to yield alcohols.

Hydrazine, H₂NNH₂: Reacts with ketones or aldehydes in the presence of potassium hydroxide to yield the corresponding alkanes (Wolif—Kishner reaction).

Hydrogen bromide, HBr: Adds to alkenes to yield alkyl bromides. Markovnikov regiochemistry is observed. Adds to alkenes in the presence of a peroxide catalyst to yield alkyl bromides. Non-Markovnikov regiochemistry is observed. Adds to alkynes to yield either bromoalkenes or 1,1-dibromoalkanes. Reacts with alcohols to yield alkyl bromides. Cleaves ethers to yield alcohols and alkyl bromides. Hydrogen chloride, HC1: Adds to alkenes to yield alkyl chlorides. Markovnikov regiochemistry is observed. Adds to alkynes to yield either chloroalkenes or 1,1-dichioroalkanes. Reacts with alcohols to yield alkyl chlorides.

Hydrogen cyanide, HCN: Adds to ketones and aldehydes to yield cyanohydrins.

Hydrogen iodide, HI: Reacts with alcohols to yield alkyl iodides (Section 17.8). Cleaves ethers to yield alcohols and alkyl iodides.

Hydrogen peroxide, H₂0₂: Oxidizes organoboranes to yield alcohols. Used in conjunction with addition of borane to alkenes, the overall transformation effects syn Markovnikov addition of water to an alkene. Oxidizes vinylic boranes to yield aldehydes. Since the vinylic borane starting materials are prepared by hydroboration of a terminal alkyne with disiamyl borane, the overall transformation is the hydration of a terminal alkyne to yield an aldehyde. Oxidizes sulfides to yield sulfoxides. Reacts with c-phenylselenenyl ketones to yield c,f3-unsaturated ketones.

Hydroxylamme, NH₂OH: Reacts with ketones and aldehydes to yield oximes. Reacts with aldoses to yield oximes as the first step in the Wohi degradation of aldoses. Hypophosphorous acid, H3P02: Reacts with arenediazonium salts to yield arenes.

Iodine, 12: Reacts with arenes in the presence of cupric chloride or hydrogen peroxide to yield iodoarenes. Reacts with carboxylic acids in the presence of lead tetraacetate to yield alkyl iodides (Hunsdiecker reaction). Reacts with methyl ketones in the presence of aqueous sodium hydroxide to yield carboxylic acids and iodoform.

lodomethane, CH₃I: Reacts with alkoxide anions to yield methyl ethers. Reacts with carboxylate anions to yield methyl esters. Reacts with enolate ions to yield a-methylated carbonyl compounds. Reacts with amines to yield methylated amines.

Iron, Fe: Reacts with nitroarenes in the presence of mineral acid to yield anilines.

Lead tetraacetate, Pb(OCOCH₃)₄: Reacts with carboxylic acids in the presence of iodine to yield alkyl iodides and carbon dioxide (Hunsdiecker reaction).

Lindlar catalyst: Acts as a catalyst for the hydrogenation of alkynes to yield cis-alkenes.

Lithium, Li: Reduces alkynes in liquid ammonia solvent to yield trans alkenes. Reacts with organohalides to yield organolithium compounds.

Lithium aluminum hydride, LiAIH₄: Reduces ketones, aldehydes, esters, and carboxylic acids to yield alcohols. Reduces amides to yield amines. Reduces alkyl azides to yield amines. Reduces nitriles to yield amines.

Lithium diisopropylamide (LDA), LiN(i-Pr)₂: Reacts with carbonyl compounds (aldehydes, ketones, esters) to yield enolate ions.

Lithium diorganocopper reagent (Gilman reagent), LiR₂Cu: Couples with alkyl halides to yield alkanes. Adds to a,1,3-unsaturated ketones to give 1,4-addition products.

Lithium tri-tert-butoxyaluminum hydride, LiA1(O-t-Bu)₃H: Reduces acid chlorides to yield aldehydes.

Magnesium, Mg: Reacts with organohalides to yield Grignard reagents.

Mercuric acetate, Hg(OCOCH₃)₂: Adds to alkenes in the presence of water, giving a-hydroxy organomercury compounds that can be reduced with sodium borohydride to yield alcohols. The overall reaction effects the Markovnikov hydration of an alkene.

Mercuric oxide, HgO: Reacts with carboxylic acids in the presence of bromine to yield alkyl bromides and carbon dioxide (Hunsdiecker reaction; Section 20.9). Mercuric sulfate, HgSO4: Acts as a catalyst for the addition of water to alkynes in the presence of aqueous sulfuric acid, yielding ketones.

Mercuric trifluoroacetate, Hg(OCOCF₃)₂: Adds to alkenes in the presence of alcohol, giving a-alkoxy organomercury compounds that can be reduced with sodium borohydride to yield ethers. The overall reaction effects a net addition of an alcohol to an alkene.

1-Mesitylenesulfonyl-3-nitro-1,2,4-triazole (MSNT): Acts as a coupling reagent for use in DNA synthesis.

Methyl sulfate, (CH₃O)₂S0₂: A reagent used to methylate heterocyclic amine bases during Maxam—Gilbert DNA sequencing.

Nitric acid, HNO₃: Reacts with arenes in the presence of sulfuric acid to yield nitroarenes.Oxidizes aldoses to yield aldaric acids.

Nitronium tetrafluoroborate, NO₂BF4: Reacts with arenes to yield nitroarenes.

Nitrous acid, HNO²: Reacts with amines to yield diazonium salts.

Osmium tetraoxide, 0s04: Adds to alkenes to yield 1,2-diols. Reacts with alkenes in the presence of periodic acid to cleave the carbon—carbon double bond, yielding ketone or aldehyde fragments.

Oxalyl chloride, C1COCOC1: Reacts with carboxylic acids, yielding acid chlorides.

Ozone, 0₃: Adds to alkenes to cleave the carbon—carbon double bond and give ozonides. The ozonides can then be reduced with zinc in acetic acid to yield carbonyl compounds. Palladium on barium sulfate, Pd/BaSO4: Acts as a hydrogenation catalyst in the Rosenmund reduction of acid chlorides to yield aldehydes.

 Palladium on carbon, Pd/C: Acts as a hydrogenation catalyst in the reduction of carbon—carbon multiple bonds. Alkenes and alkynes are reduced to yield alkanes. Acts as a hydrogenation catalyst in the reduction of aryl ketones to yield alkylbenzenes. Acts as a hydrogenation catalyst in the reduction of nitroarenes to yield anilines.

Periodic acid, H10₄: Reacts with 1,2-diols to yield carbonyl-containing cleavage products.

Peroxyacetic acid, CH₃CO₃H: Oxidizes sulfoxides to yield sulfones  Phenyl isothiocyanate, C6H5—N=C==S: A reagent used in the Edman degradation of peptides to identify N-terminal amino acids.

Phenylselenenyl bromide, C6H5SeBr: Reacts with enolate ions to yield aphenylselenenyl ketones. On oxidation of the product with hydrogen peroxide, an a,/3-unsaturated ketone is produced.

Phosphorus oxychioride, POC13: Reacts with secondary and tertiary alcohols to yield alkene dehydration products.

Phosphorus tribromide, PBr3: Reacts with alcohols to yield alkyl bromides. Reacts with carboxylic acids in the presence of bromine to yield a-bromo carboxylic acids (Hell—Volhard—Zelinskii reaction).

Phosphorus trichioride, PCl3: Reacts with carboxylic acids to yield acid chlorides.

Platinum oxide (Adam’s catalyst), Pt02: Acts as a hydrogenation catalyst in the reduction of alkenes and alkynes to yield alkanes.

Potassium tert-butoxide, K0-t-Bu: Reacts with alkyl halides to yield alkenes. Reacts with allylic halides to yield conjugated dienes in an elimination reaction. Reacts with chloroform in the presence of an alkene to yield a dichlorocyclopropane.

Potassium hydroxide, KOH: Reacts with alkyl halides to yield alkenes by an elimination reaction. Reacts with 1,1- or 1,2-dihaloalkanes to yield alkynes by a twofold elimination reaction.

Potassium nitrosodisulfonate (Fremy’s salt), (KSO3)2N0: Oxidizes phenols and anilines to yield quinones.

Potassium permanganate, KMnO4: Oxidizes alkenes under alkaline conditions to yield 1,2-diols. Oxidizes alkenes under neutral or acidic conditions to give carboxylic acid double- bond cleavage products. Oxidizes alkynes to give carboxylic acid triple-bond cleavage products. Oxidizes arenes to yield benzoic acids.

Potassium phthalimide, C6H4(CO)₂NK: Reacts with alkyl halides to yield an Nalkylphthalimide that is hydrolyzed by aqueous sodium hydroxide to yield an amine (Gabriel amine synthesis).

Pyridine, C5H5N: Reacts with a-bromo ketones to yield a,/3-unsaturated ketones. Acts as a catalyst for the reaction of alcohols with acid chlorides to yield esters.

Acts as a catalyst for the reaction of alcohols with acetic anhydride to yield acetate esters.

Pyridinium chlorochromate (PCC), C5H6NCrO3C1: Oxidizes primary alcohols to yield aldehydes and secondary alcohols to yield ketones.

Pyrrolidine, C4H8N: Reacts with ketones to yield enamines for use in the Stork enamine reaction.

Raney nickel, Ni: Reduces dithioacetals to yield alkanes by a desulfurization reaction.

Rhodium on carbon, Rh/C: Acts as a hydrogenation catalyst in the reduction of benzene rings to yield cyclohexanes.

Silver oxide, Ag20: Oxidizes primary alcohols in aqueous ammonia solution to yield aldehydes (Tollens oxidation). Acts as a catalyst for the reaction of alcohols with alkyl halides to yield ethers.

Sodium amide, NaNH2: Reacts with terminal alkynes to yield acetylide anions. Reacts with 1,1- or 1,2-dihalides to yield alkynes by a twofold elimination reaction. Reacts with aryl halides to yield anilines by a benzyne aromatic substitution mechanism.

Sodium azide, NaN3: Reacts with alkyl halides to yield alkyl azides. Reacts with acid chlorides to yield acyl azides. On heating in the presence of water, acyl azides yield amines and carbon dioxide.

Sodium bisulfite, NaHSO3: Reduces osmate esters, prepared by treatment of an alkene with osmium tetraoxide, to yield 1,2-diols.

Zinc, Zn: Reduces ozonides, produced by addition of ozone to alkenes, to yield ketones and aldehydes. Reduces disulfides to yield thiols. Reduces ketones and aldehydes in the presence of aqueous HC1 to yield alkanes (Clenimensen reduction).

Zinc bromide, ZnBr2: Acts as a Lewis acid catalyst to cleave DMT ethers in DNA synthesis.

Zinc—copper alloy, Zn(Cu): Reacts with diiodomethane in the presence of alkenes to yield cyclopropanes (Simmons—Smith reaction).