Show how you might synthesize the following compounds starting with bromobenzene, and alkyl or alkenyl halides of four carbon atoms or fewer.
a. 3-phenylprop-1-ene

Verified step by step guidance

1. Step 1: Begin with bromobenzene (C6H5Br) as the starting material. Perform a Grignard reaction by reacting bromobenzene with magnesium (Mg) in dry ether to form phenylmagnesium bromide (C6H5MgBr). This is a key organometallic intermediate.
2. Step 2: Prepare propenal (CH2=CH-CHO), which is an alkenyl compound with three carbon atoms. This can be synthesized separately if not readily available.
3. Step 3: Perform a nucleophilic addition reaction between phenylmagnesium bromide (C6H5MgBr) and propenal (CH2=CH-CHO). The Grignard reagent will attack the carbonyl carbon of propenal, forming an intermediate alcohol.
4. Step 4: Dehydrate the intermediate alcohol to form 3-phenylprop-1-ene (C6H5-CH=CH-CH2). This can be achieved using an acid catalyst, such as concentrated sulfuric acid (H2SO4), to remove water and form the double bond.
5. Step 5: Purify the product using distillation or another appropriate method to isolate 3-phenylprop-1-ene. Confirm the structure using spectroscopic techniques such as NMR or IR.

Key Concepts

Electrophilic Aromatic Substitution

Electrophilic aromatic substitution (EAS) is a fundamental reaction in organic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. In the context of synthesizing 3-phenylprop-1-ene from bromobenzene, EAS can be used to introduce a propyl group onto the benzene ring, forming a substituted aromatic compound that can further undergo elimination to yield the desired alkene.

Alkylation Reactions

Alkylation reactions involve the introduction of an alkyl group into a molecule, often through nucleophilic substitution or EAS. In this synthesis, alkyl halides can react with bromobenzene to form a new carbon-carbon bond, which is crucial for building the propyl chain needed for 3-phenylprop-1-ene. Understanding the reactivity of alkyl halides is essential for selecting the appropriate reaction conditions.

Elimination Reactions

Elimination reactions are processes where elements of the starting material are removed, resulting in the formation of a double bond. In synthesizing 3-phenylprop-1-ene, after the alkylation step, an elimination reaction can be performed to remove a leaving group and generate the alkene. This step is vital for achieving the final product with the desired double bond configuration.