Are these points true?
Dear student,
Factors that affect SN2 mechanism:
Nucleophilicity :
Because the nucleophile is involved in the rate-determining step of SN2 reactions, stronger nucleophiles react faster. Stronger nucleophiles are said to have increased nucleophilicity
In general, within a period of the periodic table, nucleophilicity increases from right to left. Furthermore, for different reagents with the same nucleophilic atom, an anion is a better nucleophile than a neutral species.
Solvent effects :
In solution the comparison of nucleophilicity vs. basicity is complicated by solvation effects. Polar aprotic solvents (e.g. acetonitrile, dimethylsulfoxide, dimethylformamide, etc.) are good at solvating cations, but not anions.
As a result, the nucleophiles are not highly solvated, and the relative order of nucleophilicities is similar to that observed in the gas phase. Polar protic solvents (e.g. alcohols, water) are much better at solvating anions, so nucleophiles are highly solvated in these solvents. The relative order of nucleophilicities can be changed dramatically by this solvation.
Solvation of nucleophiles by polar protic solvents also inhibits the nucleophile’s ability to take part in an SN2 reaction, so SN2 reactions are much slower in polar protic solvents compared with polar aprotic solvents.
Regards
Factors that affect SN2 mechanism:
Nucleophilicity :
Because the nucleophile is involved in the rate-determining step of SN2 reactions, stronger nucleophiles react faster. Stronger nucleophiles are said to have increased nucleophilicity
In general, within a period of the periodic table, nucleophilicity increases from right to left. Furthermore, for different reagents with the same nucleophilic atom, an anion is a better nucleophile than a neutral species.
Solvent effects :
In solution the comparison of nucleophilicity vs. basicity is complicated by solvation effects. Polar aprotic solvents (e.g. acetonitrile, dimethylsulfoxide, dimethylformamide, etc.) are good at solvating cations, but not anions.
As a result, the nucleophiles are not highly solvated, and the relative order of nucleophilicities is similar to that observed in the gas phase. Polar protic solvents (e.g. alcohols, water) are much better at solvating anions, so nucleophiles are highly solvated in these solvents. The relative order of nucleophilicities can be changed dramatically by this solvation.
Solvation of nucleophiles by polar protic solvents also inhibits the nucleophile’s ability to take part in an SN2 reaction, so SN2 reactions are much slower in polar protic solvents compared with polar aprotic solvents.
Regards