Methods of Amine Preparation

Vocabulary flashcards covering methods of amine synthesis from alkyl halides, alcohols, nitriles, amides, oximes, nitroalkanes, and isocyanides based on the lecture notes.

Hoffmann's Ammonolysis (Excess Ammonia)

The reaction of an alkyl halide ($R-X$) with excess ammonia ($NH_3$) under heating ($\Delta$) to yield a primary amine ($1^\circ\text{ amine}$): $R-X + NH_3 \xrightarrow{\Delta} R-NH_2$.

Hoffmann's Ammonolysis (Excess Alkyl Halide)

The reaction of excess alkyl halide ($R-X$) with ammonia ($NH_3$) under heating ($\Delta$) to produce a mixture of primary, secondary, tertiary amines, and ultimately a quaternary ammonium salt ($4^\circ\text{ amine}$): $R-X + NH_3 \xrightarrow{\Delta} R-NH_2 \xrightarrow{R-X} R-NH-R \xrightarrow{R-X} R_3N \xrightarrow{R-X} R_4N^+ X^-$.

Preparation of Primary Amine from Alcohol

The reaction of an alcohol ($R-OH$) with excess ammonia ($NH_3$) heated over an alumina catalyst ($Al_2O_3$) to yield a primary amine ($1^\circ\text{ amine}$) and water: $R-OH + NH_3 \xrightarrow[\Delta]{Al_2O_3} R-NH_2 + H_2O$.

Preparation of Tertiary Amine from Alcohol

The reaction of excess alcohol ($R-OH$) with ammonia ($NH_3$) over alumina ($Al_2O_3$) under heating/dehydration to yield secondary and tertiary amines: $R-OH + NH_3 \xrightarrow[\text{Dehydration}]{Al_2O_3, \Delta} R-NH_2 \xrightarrow{R-OH} R-NH-R \xrightarrow{R-OH} R_3N$.

Reduction of Nitriles (Cyanides)

The reduction of alkyl cyanides ($R-C \equiv N$) using $LiAlH_4 / H^+$ or $Na / EtOH$ or $H_2 / Pt / Pd$ to yield a primary amine ($1^\circ\text{ amine}$): $R-C \equiv N \xrightarrow{LiAlH_4 / H^+} R-CH_2-NH_2$.

Reduction of Amides

The reduction of amides ($R-C(=O)-NH_2$) using $LiAlH_4 / H^+$ to yield a primary amine ($1^\circ\text{ amine}$): $R-C(=O)-NH_2 \xrightarrow{LiAlH_4 / H^+} R-CH_2-NH_2$.

Reduction of Oximes

The reduction of oximes ($R-CH=N-OH$) using $LiAlH_4 / H^+$ to yield a primary amine ($1^\circ\text{ amine}$): $R-CH=N-OH \xrightarrow{LiAlH_4 / H^+} R-CH_2-NH_2$.

Reduction of Nitroalkanes

The reduction of nitro compounds ($R-CH_2-NO_2$) using $Sn / HCl$, $Zn / HCl$, or $H_2 / Pt$ to yield a primary amine ($1^\circ\text{ amine}$): $R-CH_2-NO_2 \xrightarrow{Sn / HCl} R-CH_2-NH_2$.

Reduction of Isocyanides (Isonitriles)

The reduction of alkyl isocyanides ($R-N \equiv C$) using $LiAlH_4 / H^+$ to yield a secondary amine ($2^\circ\text{ amine}$): $R-N \equiv C \xrightarrow{LiAlH_4 / H^+} R-NH-CH_3$.

Cyanide vs. Isocyanide Reduction Rule

Reduction of alkyl cyanides ($R-C \equiv N$) produces a primary amine ($1^\circ\text{ amine}$), whereas reduction of alkyl isocyanides ($R-N \equiv C$) produces a secondary amine ($2^\circ\text{ amine}$).