Question

Using your old and new reaction roadmaps as a guide, show how to convert ethane into 1-butanol.You must use ethane as the source of all carbon atoms in the target molecule. Show all reagents and all molecules synthesized along the way.

Short answer

Answer: Ethane can be converted into 1-butanol through a series of reactions. First, ethane is converted into ethyl bromide using N-bromosuccinimide (NBS). Then, a Grignard reaction with ethylene oxide extends the carbon chain, producing 1-propanol. This 1-propanol is then transformed into 1-propyl bromide using thionyl bromide (SOBr2) or phosphorus tribromide (PBr3). Finally, another Grignard reaction with formaldehyde and subsequent hydrolysis yield the desired 1-butanol product.

Step-by-step solution

Formation of ethyl bromide from ethane

To form an alkyl halide from ethane, bromine is used as a halogenating agent. To perform this reaction, we will use N-bromosuccinimide (NBS) as a source of bromine. This will convert ethane into ethyl bromide. Reaction: C_2H_6 + NBS -> C_2H_5Br + HBr + succinimide

Chain extension using Grignard reaction

The ethyl bromide produced in the previous step will be converted into Grignard reagent using magnesium metal in an ether solvent. The Grignard reagent will then react with ethylene oxide, resulting in a three-carbon alcohol after hydrolysis. 1) Reaction to form Grignard reagent (ethyl magnesium bromide): C_2H_5Br + Mg -> C_2H_5MgBr 2) Reaction with ethylene oxide: C_2H_5MgBr + C_2H_4O -> C_2H_5-(CH_2)_2OMgBr 3) Hydrolysis: C_2H_5-(CH_2)_2OMgBr + H_2O -> C_2H_5-(CH_2)_2OH + Mg(OH)Br

Converting 1-propanol to 1-propyl bromide

The three-carbon alcohol obtained in step 2, 1-propanol, will be converted into 1-propyl bromide using thionyl bromide (SOBr_2) or phosphorus tribromide (PBr_3). Reaction: C_2H_5-(CH_2)_2OH + PBr_3/ SOBr_2 -> C_2H_5-(CH_2)_2Br + byproducts

Chain extension of 1-propyl bromide to 1-butene

The obtained 1-propyl bromide in step 3 will undergo a Grignard reaction using magnesium, followed by a reaction with formaldehyde and hydrolysis to obtain 1-butanol. 1) Reaction to form Grignard reagent (propyl magnesium bromide): C_2H_5-(CH_2)_2Br + Mg -> C_2H_5-(CH_2)_2MgBr 2) Reaction with formaldehyde: C_2H_5-(CH_2)_2MgBr + CH_2O -> C_2H_5-(CH_2)_3OMgBr 3) Hydrolysis: C_2H_5-(CH_2)_3OMgBr + H_2O -> C_2H_5-(CH_2)_3OH + Mg(OH)Br The final product obtained is 1-butanol, with all carbon atoms being sourced from ethane.