Reaction mechanisms

Written by Dr. Ayesha Nadeem (Chemistry)

NET · Chemistry · 5 questions

Name: ____________________ Date: ____________

The rate of an SN1 reaction depends on:
- A Both the substrate and the nucleophile
- B The concentration of the alkyl halide only
- C The concentration of the nucleophile only
- D The temperature only
An SN2 reaction at a chiral carbon results in:
- A Retention of configuration
- B A racemic mixture only
- C Inversion of configuration
- D No substitution
Heating ethanol with concentrated sulphuric acid at 170 degrees C gives mainly:
- A Ethanal
- B Diethyl ether
- C Ethene
- D Ethane
What is needed to start the chlorination of methane by a free radical mechanism?
- A A platinum catalyst
- B Ultraviolet light
- C Aqueous sodium hydroxide
- D A strong base
Which of these is a nucleophile?
- A OH-
- B AlCl3
- C NO2+
- D H+

Answer key

1. B, 2. C, 3. C, 4. B, 5. A

The slow step is the formation of a carbocation, which involves only the substrate.
The nucleophile attacks from the side opposite the leaving group, which inverts the configuration.
At this temperature the acid dehydrates the alcohol to an alkene. A lower temperature favours the ether.
Ultraviolet light splits chlorine molecules into chlorine atoms, which start the chain.
A nucleophile donates a pair of electrons. The hydroxide ion has lone pairs, while the other three are electron-poor.