brodidit for students
Home / Practice / NET / Chemistry / Reaction mechanisms
Reaction mechanisms
5 NET Chemistry questions with answers and explanations.
-
The rate of an SN1 reaction depends on:
- 1 Both the substrate and the nucleophile
- 2 The concentration of the alkyl halide only
- 3 The concentration of the nucleophile only
- 4 The temperature only
Show answer
Correct answer: The concentration of the alkyl halide only
The slow step is the formation of a carbocation, which involves only the substrate.
-
An SN2 reaction at a chiral carbon results in:
- 1 Retention of configuration
- 2 Inversion of configuration
- 3 A racemic mixture only
- 4 No substitution
Show answer
Correct answer: Inversion of configuration
The nucleophile attacks from the side opposite the leaving group, which inverts the configuration.
-
Heating ethanol with concentrated sulphuric acid at 170 degrees C gives mainly:
- 1 Ethene
- 2 Ethane
- 3 Diethyl ether
- 4 Ethanal
Show answer
Correct answer: Ethene
At this temperature the acid dehydrates the alcohol to an alkene. A lower temperature favours the ether.
-
What is needed to start the chlorination of methane by a free radical mechanism?
- 1 Ultraviolet light
- 2 A strong base
- 3 Aqueous sodium hydroxide
- 4 A platinum catalyst
Show answer
Correct answer: Ultraviolet light
Ultraviolet light splits chlorine molecules into chlorine atoms, which start the chain.
-
Which of these is a nucleophile?
- 1 H+
- 2 OH-
- 3 AlCl3
- 4 NO2+
Show answer
Correct answer: OH-
A nucleophile donates a pair of electrons. The hydroxide ion has lone pairs, while the other three are electron-poor.