Question

Show how to convert palmitic acid (hexadecanoic acid) into the following. (a) Ethyl palmitate (b) Palmitoyl chloride (c) 1-Hexadecanol (cetyl alcohol) (d) 1-Hexadecanamine (e) \(\mathrm{N}, \mathrm{N}\)-Dimethylhexadecanamide

Short answer

In summary, to convert palmitic acid to the various derivatives: (a) Ethyl palmitate: Perform esterification using ethanol and concentrated sulfuric acid as a catalyst. (b) Palmitoyl chloride: Use thionyl chloride (SOCl2) as a reagent. (c) 1-Hexadecanol (cetyl alcohol): Perform reduction using lithium aluminum hydride (LiAlH4) as a reducing agent. (d) 1-Hexadecanamine: Convert the acid into an amide, followed by reducing the amide using lithium aluminum hydride (LiAlH4). (e) N, N-Dimethylhexadecanamide: Convert the acid into the amide, followed by methylation of the amide nitrogen using methyl iodide (CH3I) and potassium carbonate (K2CO3) as a base.

Step-by-step solution

(a) Conversion to Ethyl Palmitate

To convert palmitic acid to ethyl palmitate, perform an esterification reaction using ethanol and an acid catalyst like concentrated sulfuric acid. 1. Mix palmitic acid with ethanol in a flask 2. Add a few drops of concentrated sulfuric acid as a catalyst 3. Heat the mixture under reflux until the reaction is complete 4. Cool the mixture and separate the product via simple distillation You will end up with ethyl palmitate as the final product.

(b) Conversion to Palmitoyl Chloride

To convert palmitic acid to palmitoyl chloride, use thionyl chloride (SOCl2) as a reagent. 1. Mix palmitic acid with thionyl chloride in a flask 2. Heat the mixture under reflux until the reaction is complete 3. Cool the mixture and remove any excess thionyl chloride and sulfur dioxide (SO2) byproduct by simple distillation You will obtain palmitoyl chloride as the final product.

(c) Conversion to 1-Hexadecanol (Cetyl Alcohol)

To convert palmitic acid to 1-hexadecanol, perform reduction using lithium aluminum hydride (LiAlH4) as a reducing agent. 1. Dissolve palmitic acid in an appropriate solvent such as THF or ether 2. Slowly add a solution of lithium aluminum hydride in the same solvent, with stirring and cooling 3. Heat the mixture under gentle reflux for an extended period of time until the reaction is complete 4. Cool the mixture and then cautiously add excess water to quench unreacted LiAlH4 5. Separate the organic layer containing 1-hexadecanol by simple distillation You will obtain 1-hexadecanol as the final product.

(d) Conversion to 1-Hexadecanamine

To convert palmitic acid to 1-hexadecanamine, first convert the acid into its corresponding amide and then reduce the amide. 1. Convert the acid into an acid chloride using thionyl chloride (as described in part (b)) 2. React the obtained palmitoyl chloride with excess ammonia in a flask 3. The reaction will lead to the formation of the amide, hexadecanamide 4. Perform reduction using lithium aluminum hydride (as described in part (c)) You will obtain 1-hexadecanamine as the final product.

(e) Conversion to N, N-Dimethylhexadecanamide

To convert palmitic acid to N, N-dimethylhexadecanamide, convert the acid into the amide first, followed by methylation of the amide nitrogen. 1. Convert the acid into hexadecanamide (as described in step 1 to 3 of part (d)) 2. Dissolve the obtained hexadecanamide in a suitable solvent, such as THF 3. Add excess methyl iodide (CH3I) and a mild base like potassium carbonate (K2CO3) 4. Heat the mixture under reflux until the reaction is complete 5. Carefully separate the product by simple distillation You will obtain N, N-dimethylhexadecanamide as the final product.