OZ jk(ii)lm: Amines, haloalkanes; nucleophilic substitution

Question 1

1. State the functional group to which this molecule belongs: CH₃CHClCF₃.
2. Name the molecule.

Answer 1

1. Haloalkanes
2. 2-chloro-1,1,1-trifluoropropane

Alphabetical order is prioritised over numerical

Question 2

1. To which functional group do the following molecules belong?
2. Name each.

Answer 2

1. Amines
2. Methylamine, ethylamine, propylamine

Question 3

Define substitution.

Answer 3

A reaction in which an atom or group in a molecule is replaced by another.

Question 4

What is a nucleophile?

Answer 4

An anion, or molecule with a partial negative charge, which can donate a lone pair of electrons to a positively charged atom to form a dative covalent bond.

Question 5

Draw the mechanism for the heterolytic fission of 2-chloro-2-methylpropane.

Answer 5

Forms a carbocation + a chloride

Question 6

1. What mechanism occurs during the reaction between haloalkanes and hydroxide ions?
2. State the conditions required.
3. What is the organic product?

Answer 6

1. Nucleophilic substitution
2. Reflux, ethanolic NaOH
3. Alcohols

Question 7

Draw and describe the mechanism for the substitution reaction between hydroxide ions and 1-bromobutane.

Answer 7

• C-Br bond is polar
• OH^-, nucleophile, attacks δ⁺ carbon, and donates a lone pair of electrons to form a dative covalent bond
• Heterolysis of C-Br bond forms a Br^- ion

Question 8

1. What mechanism occurs during the reaction between haloalkanes and water?
2. Give the name of this reaction.
3. State the conditions required.
4. What is the organic product?

Answer 8

1. Nucleophilic substitution
2. Hydrolysis
3. Reflux
4. Alcohols

Question 9

Draw the mechanism for the substitution reaction between water and 1-bromobutane.

Answer 9

Question 10

Write the equation for the reaction between 2-chloro-2-methylpropane and water.

Answer 10

CH₃-C(CH₃)Cl-CH₃ + H₂O → CH₃-C(CH₃)(OH)-CH₃ + HCl

Question 11

1. What mechanism occurs during the reaction between haloalkanes and ammonia?
2. State the conditions required.
3. What is the organic product?

Answer 11

1. Nucleophilic substitution
2. Heat in sealed tube, with conc. NH₃(aq)
3. Amines

Question 12

Explain this mechanism.

Answer 12

• C-Br bond is polar
• Ammonia, nucleophile, attacks δ⁺ carbon and donates a lone pair of electrons to form a dative covalent bond
• Heterolysis of C-Br bond produces Br^- ion
• Nitrogen has charge +1 so repels the δ⁺ hydrogens bonded to it; one proton dissociates
• Forms ethylamine + HBr

Question 13

1. What mechanism occurs during the reaction between alcohols and halide ions?
2. State the conditions required.
3. What is the organic product?

Answer 13

1. Nucleophilic substitution
2. HCl or H₂SO₄
3. Haloalkanes

Question 14

1. Draw the mechanism for the reaction between butan-1-ol and bromide ions, in the presence of acid.
2. Suggest why the reaction is catalysed by an acid.

Answer 14

• Acid dissociates, protonating the hydroxyl group
• C-Br bond becomes more polar
• Carbon has a greater partial positive charge
• More susceptible to nucleophilic attack