Question

Draw the organic product of the following reaction between (1S,3S)-1-chloro-3-methylcyclopentane and methanethiol in the presence of sodium hydroxide. Show any H's on chirality centers, if applicable, and use wedge-and-dash bonds.

Answer 1

Concepts and reason

Primary and secondary alkyl halides undergo reactions with strong nucleophiles. Alkyl halides react with thiols to form sulphides. Here, the reaction follows through mechanism.

reactions are concerted and form a product with an inverted configuration.

Asymmetric carbon (chiral centre) can be identified, when the carbon atom is bonded with four different groups or atoms. Assign the R and S configurations to the asymmetric carbon atoms.

Fundamentals

Alkyl halide acts as substrate and thiol acts as a nucleophile, and base NaOH acts as catalyst.

This reaction occurs in two steps. They are,

1.Nucleophile generation

2.Nucleophilic attack on the substrate

Chirality centre: An atom (usually carbon) which is bonded to four different atoms or groups is known as chiral centre. In general, it is represented with an asterisk (*).

R and S configuration can be assign to the compound by using the following CIP (Cahn-Ingold-Prelog) sequence rules:

Rule 1: Select the chiral centre in the compound and assign priorities to the atoms based on its atomic number. The atom which is having highest atomic number gets the priority and atom which is having least atomic number (usually hydrogen) gets fourth priority.

Rule 2: If the isotopes of same atom are attached to the chiral centre, then the atom with the higher atomic mass receives higher priority.

Rule 3: If the first atom of each substituent is same then give priority to the second atom in each substituent.

Rule 4: If the substituents have multiple bonds, then the multiple bonded atoms are considered as same number of single boned atoms.

If the rotation of the numbering is in clockwise direction, then the configuration of the isomer is R. Similarly, if the rotation of the numbering is in anticlockwise direction, then the configuration of the isomer is S.

Consider the reaction between NaOH and Thiol as shown below:

Consider the reaction of given compound with the nucleophile generated to form the substitution product as shown below:

Ans:

Hence, the organic product of the given reaction is shown below:

The product of the reaction is characterized as R, S and chiral.