Question

Using your roadmaps as a guide, show how to convert (2-bromoethyl) benzene into 2-chloro-1-phenylethanone. Show all reagents and all molecules synthesized along the way.

Short answer

Answer: The reagents required for this conversion are Sodium Chloride (NaCl), Chromic Acid (H2CrO4), and Sodium Hydroxide (NaOH). The products formed during this process are (2-Chloroethyl)benzene, Sodium Bromide (NaBr), 2-Chloro-1-phenylethanone, Sodium Chromate (NaCrO4), and Water (H2O).

Step-by-step solution

Substitution of Bromine with Chlorine

To convert (2-bromoethyl) benzene to 2-chloroethylbenzene, we will carry out a nucleophilic substitution reaction using Sodium Chloride (NaCl) as our nucleophile. The reaction can be represented as follows: (2-Bromoethyl)benzene + NaCl ⟶ (2-Chloroethyl)benzene + NaBr

Oxidation of 2-Chloroethylbenzene to 2-Chloro-1-phenylethanone

In order to convert 2-chloroethylbenzene into 2-chloro-1-phenylethanone, we need to oxidize the ethyl group to a carbonyl group. This can be achieved using the oxidizing agent chromic acid (H2CrO4) in the presence of a base such as sodium hydroxide (NaOH). The reaction can be represented as follows: (2-Chloroethyl)benzene + H2CrO4 + NaOH ⟶ 2-Chloro-1-phenylethanone + NaCrO4 + H2O In conclusion, we have successfully converted (2-bromoethyl) benzen

Reagents and molecules synthesized

The necessary reagents for this conversion are: 1. Sodium Chloride (NaCl) - for the nucleophilic substitution reaction 2. Chromic Acid (H2CrO4) - an oxidizing agent to oxidize the ethyl group 3. Sodium Hydroxide (NaOH) - a base to facilitate the oxidation The molecules synthesized during this process are: 1. (2-Chloroethyl)benzene - the intermediate product formed after the nucleophilic substitution reaction 2. Sodium Bromide (NaBr) - a byproduct of the nucleophilic substitution reaction 3. 2-Chloro-1-phenylethanone - the final product 4. Sodium Chromate (NaCrO4) - a byproduct of the oxidation reaction 5. Water (H2O) - a byproduct of the oxidation reaction

Key concepts

Nucleophilic Substitution

Nucleophilic substitution reactions play a crucial role in organic synthesis. These reactions involve the replacement of an atom or a group within a molecule by a nucleophile, which is an atom or molecule with a free pair of electrons. In the example provided in the exercise, Sodium Chloride (NaCl) is used as the nucleophile.
NaCl attacks the carbon that is bonded to the bromine in (2-bromoethyl) benzene. Bromine is a good leaving group, meaning it can detach easily, which facilitates the substitution process. As a result, bromine leaves, and chloride takes its place, resulting in the formation of (2-chloroethyl) benzene. This type of reaction is classified as a bimolecular nucleophilic substitution or SN2 reaction.

• In SN2 reactions, the rate depends on the concentration of both the substrate and the nucleophile.
• The reaction results in a direct one-step mechanism without intermediate formation.
• The substitution inverts the configuration of the substrate, important in chiral compounds.

Understanding nucleophilic substitution is fundamental in transforming simple substrates into more complex organic molecules.

Oxidation Reaction

Oxidation reactions are transformations where an organic molecule loses electrons, typically incorporating oxygen or losing hydrogen. In the exercise example, (2-chloroethyl) benzene is oxidized to 2-chloro-1-phenylethanone. This is achieved with chromic acid (H2CrO4) in the presence of a base, sodium hydroxide (NaOH).
The oxidation converts the ethyl group attached to benzene into a carbonyl group, specifically a ketone. This occurs because chromic acid is a strong oxidizing agent capable of transforming secondary alcohols and alkyl groups into carbonyl compounds. Key to this reaction:

• Chromic acid provides the necessary oxygen atoms to form the carbonyl group.
• Sodium hydroxide acts to neutralize any acidic conditions harming the reaction progress.
• This reaction exemplifies a classic oxidation in organic chemistry, where a single bond is converted to a double bond with oxygen.

Mastering oxidation reactions allows chemists to create functional groups that are vital for further chemical transformations.

Reagents and Byproducts

In any chemical synthesis, choosing the appropriate reagents is critical to achieving desired transformations. When converting (2-bromoethyl) benzene to 2-chloro-1-phenylethanone, specific reagents are used purposefully for each reaction stage.
Sodium Chloride (NaCl) is the reagent for the nucleophilic substitution step, aiding in replacing bromine with chlorine. Chromic Acid (H2CrO4), a robust oxidizing agent, helps in the oxidation phase, transforming the alkyl group into a ketone.

• Sodium Hydroxide (NaOH) plays a supportive role by maintaining neutral pH conditions during oxidation, ensuring the reaction proceeds efficiently.
• Byproducts like Sodium Bromide (NaBr) form from substitution, whereas Sodium Chromate (NaCrO4) and Water (H2O) result from the oxidation step.

Awareness of both the main reagents and the molcules synthesized and byproducts formed give insight into reaction efficiency and potential environmental impacts. Balancing effective chemistry with sustainability considerations remains a cornerstone of modern chemical synthesis.