7. Between ethanol, ethylamine and ethanethiol, which is the most nucleophilic:
a. ethanol
b. ethylamine
c. ethanethiol
d. Both ethylamine and ethanethiol are equally nucleophilic
Ethylamine is the most nucleophilic among ethanol, ethylamine, and ethanethiol.
Option Analysis
Ethanol (CH₃CH₂OH): Oxygen holds lone pairs tightly due to high electronegativity (3.5), reducing electron donation ability. Neutral alcohols show weak nucleophilicity in SN2 reactions.
Ethylamine (CH₃CH₂NH₂): Nitrogen (electronegativity 3.0) is less electronegative than oxygen, with a lone pair readily available. Amines rank higher than alcohols in nucleophilicity when comparing same-row atoms, paralleling basicity trends.
Ethanethiol (CH₃CH₂SH): Sulfur (electronegativity 2.5) offers higher polarizability, enhancing nucleophilicity over oxygen in protic solvents for anions. However, neutral thiols trail amines due to basicity differences.
This -style question tests neutral molecule nucleophilicity. Ethylamine leads due to nitrogen’s optimal electron density versus oxygen’s tight hold and sulfur’s lower basicity in neutral form.
