Question

Which alkyl chloride, through primary, is essentially unreactive in sn2 reactions?

Answer 1

In SN2 reactions, primary alkyl chlorides are generally reactive, but steric hindrance can cause some to be less reactive. Alkyl chlorides with neighboring bulky groups can be unreactive in SN2 due to restricted access for nucleophiles. Tertiary alkyl halides are typically unreactive in SN2 reactions, preferring SN1 or E1 mechanisms.

Step-by-step explanation:

The student's question asks which alkyl chloride is essentially unreactive in SN2 reactions when considering primary alkyl chlorides. SN2 reactions involve a nucleophile attacking the carbon centre and displacing the leaving group, typically a halide, through a concerted mechanism with inversion of stereochemistry. This mechanism is characteristic of primary and methyl alkyl halides, with important factors being the steric accessibility of the central carbon and the strength of the leaving group.

However, among primary alkyl chlorides, alkyl chlorides with increased steric hindrance due to neighbouring substituents can be less reactive in SN2 reactions. While a standard primary alkyl chloride like ethyl chloride is typically reactive in SN2 reactions, bulkier substrates that are still considered primary may react slower or not at all. An example could be a primary alkyl chloride with adjacent bulky groups that restrict the approach of the nucleophile, leading to steric hindrance. However, without further structural information about specific alkyl chlorides, standard primary alkyl chlorides like methyl chloride or ethyl chloride do not exhibit this unreactivity in SN2 reactions.

In contrasting SN1 and SN2 mechanisms, the ease of nucleophilic attack plays a significant role. Tertiary alkyl halides are more prone to SN1 and E1 mechanisms due to their highly hindered nature which impedes nucleophilic attack, making them unsuitable for SN2 reactions. Conversely, primary alkyl halides are typically more reactive in SN2 reactions. It is important to note that in SN1 reactions, the rate-determining step is unimolecular, involving the formation of a carbocation intermediate. This intermediate is planar, allowing for nucleophilic attack on either side which can lead to a racemic mixture if the original molecule was chiral.

Answer 2

Nucleophilic acyl substitution describe a class of substitution reactions involving nucleophiles and acyl compounds. In this type of reaction, a nucleophile – such as an alcohol, amine, or enolate – displaces the leaving group of an acyl derivative – such as an acid halide, anhydride, or ester. The resulting product is a carbonyl-containing compound in which the nucleophile has taken the place of the leaving group present in the original acyl derivative. Because acyl derivatives react with a wide variety of nucleophiles, and because the product can depend on the particular type of acyl derivative and nucleophile involved, nucleophilic acyl substitution reactions can be used to synthesize a variety of different products.