Alpha-halogenation

α-Halogenation (acidic): 4,4-dimethyl-2-pentanone (a methyl ketone) with Br2; MeOH gives 1-bromo-4,4-dimethylpentan-2-one (the α-halo ketone). 89% yield.

Hell–Volhard–Zelinsky: hexanoic acid (a carboxylic acid) with Br2, Δ; PCl3 (cat.) gives 2-bromohexanoic acid (the α-bromo acid).

Haloform: pinacolone (a methyl ketone) with excess; NaOH; Br2 gives pivalic acid (the carboxylic acid). 74% yield.

α-Halogenation (basic): 5,6-difluoro-1-indanone (an aryl ketone) with 2 equiv Br2, KOH gives 2,2-dibromo-5,6-difluoro-3H-inden-1-one (the α-halo ketone).

Silyl enol ether halogenation: trimethyl-(2-methyl-1-methylene-propoxy)-silane (a silyl enol ether) with Br2; Hexane (solvent) gives 1-bromo-3-methylbutan-2-one (the α-halo ketone). 79% yield.

α-Halogenation (acidic): acetone (a methyl ketone) with Br2; AcOH gives bromoacetone (the α-halo ketone). 92% yield.

Hell–Volhard–Zelinsky: lauric acid (a carboxylic acid) with Br2; PCl3 gives 2-bromododecanoic acid (the α-bromo acid).

Haloform: an α-halo ketone with 2 equiv. Br2; Na2CO3 gives 9H-fluorene-2,7-dicarboxylic acid. 100% yield.

α-Halogenation (acidic): cyclohexanone (a six-membered cyclic ketone) with Cl2, H2O gives 2-chlorocyclohexanone (the α-halo ketone).

Hell–Volhard–Zelinsky: isovaleric acid (a carboxylic acid) with Br2; PCl3, Δ gives 2-bromoisovaleric acid (the α-bromo acid).

α-Halogenation (acidic): 3-methyl-2-butanone (a methyl ketone) with Br2, CH3OH; 0-10 °C gives 1-bromo-3-methylbutan-2-one (the α-halo ketone).

Hell–Volhard–Zelinsky: isocaproic acid (a carboxylic acid) with Br2; PCl3, Δ gives 2-bromo-4-methylpentanoic acid (the α-bromo acid).

α-Halogenation (acidic): 2-methylcyclohexanone (a six-membered cyclic ketone) with SO2Cl2; CCl4 gives 2-chloro-2-methylcyclohexan-1-one (the α-halo ketone).

α-Halogenation (acidic): benzylmalonic acid (a carboxylic acid) with Br2; CH3CH2OCH2CH3 gives 2-benzyl-2-bromopropanedioic acid (the α-halo acid).

Hell–Volhard–Zelinsky: gamma-butyrolactone (a five-membered lactone) with P, Br2; Δ gives 3-bromooxolan-2-one (the α-bromo acid).

α-Halogenation (acidic): p-bromoacetophenone (an aryl ketone) with Br2; AcOH gives 4-bromophenacyl bromide (the α-halo ketone).

Hell–Volhard–Zelinsky: hexanoic acid (a carboxylic acid) with 1) SOCl2, CCl4, 65 °C; 2) NBS, HBr, 85 °C gives 2-bromohexanoyl chloride (the α-bromo acid).

α-Halogenation (acidic): acetone (a methyl ketone) with Br2; AcOH, H2O gives bromoacetone (the α-halo ketone).

α-Halogenation (acidic): 1,3-diphenyl-2-propanone (a dialkyl ketone) with Br2, AcOH gives 1,3-dibromo-1,3-diphenylpropan-2-one (the α-halo ketone).

α-Halogenation (acidic): diethyl malonate (a malonate ester) with Br2, hν; CCl4, Δ gives diethyl bromomalonate (the α-halo ester).

α-Halogenation (acidic): phenylacetone (a methyl ketone) with Br2; benzene gives 1-bromo-1-phenylpropan-2-one (the α-halo ketone).

α-Halogenation (acidic): 1-(3-fluoro-4-(methylsulfonyl)phenyl)propan-2-one (a methyl ketone) with Br2; dioxane (solvent) gives the α-halo ketone. 85% yield.

α-Halogenation (acidic): pinacolone (a methyl ketone) with 2 equiv Br2, MeOH gives 1,1-dibromo-3,3-dimethyl-2-butanone (the α-halo ketone). 75% yield.

Hell–Volhard–Zelinsky: 2-methyldodecanoic acid (a carboxylic acid) with Br2, PBr3; 90 °C gives 2-bromo-2-methyldodecanoyl bromide (the α-bromo acid).

Hell–Volhard–Zelinsky: isobutyric acid (a carboxylic acid) with P, Br2; 100 °C gives 2-bromo-2-methylpropionyl bromide (the α-bromo acid).