QUESTION 4 (10 marks)
Consider the organic molecule shown.
H3C C CH2 H3C
a) Identify the molecule as saturated or unsaturated.
[1 mark]
b) Apply IUPAC rules to name this molecule.
[1 mark]
c) Write an equation to show the products formed by the hydration of this molecule.
[2 marks]
d) Predict which is the major product formed in c).
[1 mark]
e) Identify a physical property and experimental technique that could be used to separate products formed by hydration in c). Explain your reasoning.
[5 marks]
QCAA guide · typeset solution
QCAA sample response and mark allocation
4 | a) | unsaturated | • provides unsaturated [1 mark] | |
b) | 2–methylpropene | • provides 2- methylpropene [1 mark] |
c) | 2(CH3)2C = CH2 + 2H2O HH+⎯ (CH3)3C(OH) + (CH3)2CHCH2OH | • identifies (CH3)3C(OH) as a product [1 mark] • identifies (CH3)2CHCH2OH as a product [1 mark] | Accept condensed or expanded structural formula. | |
d) | Major product (Markovnikov’s rule) (CH3)3C(OH) | • identifies tertiary alcohol as the major product produced [1 mark] | ||
e) | (CH3)2CHCH2OH is a primary alcohol and (CH3)3C(OH) is a tertiary alcohol. Therefore, they have different boiling points. Experimental technique: distillation The hydroxyl group of a primary alcohol is more exposed than it is in a tertiary alcohol, therefore is easier for the primary alcohol to form more hydrogen bonds. Therefore, the intermolecular forces are stronger and the boiling point higher for (CH3)2CHCH2OH. | • identifies the products are primary and tertiary alcohols [1 mark] • identifies boiling point as physical property that can be used to separate the alcohols [1 mark] • identifies distillation as a suitable experimental technique [1 mark] • links the position of the hydroxyl group in the primary alcohol to increased hydrogen bonding [1 mark] • indicates that stronger intermolecular forces result in a higher boiling point for the primary alcohol [1 mark] |
QCAA sample response and marking criteria reproduced from the official guide.
Compare your working with the guide above.