Provide the reagents necessary to carry out the following conversions.

Question: 1. Provide the reagents necessary to carry out the following conversions.

Provide the reagents necessary to convert an alkyl bromide (–CH₂–Br) to a carboxylic acid (–COOH).

Answer1: Reagents: Step 1: NaCN (to form the nitrile). Step 2: Acidic hydrolysis (e.g., H₃O⁺, heat) to convert the nitrile to a carboxylic acid.

Question: 2. Provide the reagents necessary to carry out the following conversions.

Provide the reagents necessary to convert an alkyl bromide (–CH₂–Br) to an alcohol (–CH₂–OH).

Answer2: Reagents: A strong nucleophile like NaOH (aqueous) to substitute Br with OH.

Question: 3. Provide a stepwise synthesis of a tertiary benzylic alcohol using benzyl alcohol as your only source of carbon and any other necessary reagents.

Answer3. Stepwise Synthesis:

a) Oxidize a portion of benzyl alcohol (C₆H₅CH₂OH) to benzaldehyde (C₆H₅CHO) using a mild oxidant (e.g., PCC).
b) Convert another portion of benzyl alcohol to benzyl bromide (C₆H₅CH₂Br) using PBr₃.
c) Form benzylmagnesium bromide (C₆H₅CH₂MgBr) by reacting benzyl bromide with Mg in dry ether.
d) Add benzylmagnesium bromide to benzaldehyde to form a secondary benzyl alcohol.
e) Oxidize the secondary alcohol to a ketone using a suitable oxidant (e.g., Jones reagent or PCC).
f) Add another equivalent of benzylmagnesium bromide to the ketone to form the desired tertiary benzylic alcohol.

Explanation:

Step 1: Converting Alkyl Bromide to Carboxylic Acid

Alkyl bromides can be converted to nitriles using NaCN (via SN2). Subsequent acidic hydrolysis of the nitrile yields the corresponding carboxylic acid.

Step 2: Converting Alkyl Bromide to Alcohol

A primary alkyl bromide can be substituted by the hydroxide ion (NaOH in water) to give the corresponding alcohol via an SN2 mechanism.

Step 3: Synthesizing a Tertiary Benzylic Alcohol from Benzyl Alcohol

• Oxidation of benzyl alcohol to benzaldehyde provides an aldehyde for nucleophilic addition.
• Formation of benzylmagnesium bromide from benzyl bromide allows nucleophilic addition to carbonyl compounds.
• Sequential steps (forming a secondary alcohol from the aldehyde, oxidation to a ketone, and then another nucleophilic addition) yield a tertiary alcohol, using only benzyl alcohol as the carbon source.

Extended Knowledge:

Nitrile Formation and Hydrolysis

Nitriles (–CN) can be prepared from alkyl halides using NaCN. They can be hydrolyzed to carboxylic acids under acidic or basic conditions, providing a route from haloalkanes to carboxylic acids.

Grignard Reagents

Grignard reagents (RMgX) are formed by reacting alkyl or aryl halides with magnesium in anhydrous ether. They are strong nucleophiles that add to aldehydes and ketones to form alcohols. This allows for constructing complex carbon skeletons from simpler precursors.