Older MCQs might not have the typical A, B, C,
D
choices. They
have choices 1, 2, 3, and a combination of them is the answer. Below is the key that maps such
combinations to the answer.
A
1, 2 and 3 are correct
B
1 and 2 only are correct
C
2 and 3 only are correct
D
1 only is correct
recall the reactions (including reagents and conditions) by which alkenes can be produced: (a) elimination of HX from a halogenoalkane by ethanolic NaOH and heat (b) dehydration of an alcohol, by using a heated catalyst (e.g. \( Al_2O_3 \)) or a concentrated acid (e.g. concentrated \( H_2SO_4 \)) (c) cracking of a longer chain alkane
describe: (a) the reaction with oxygen (combustion) (b) substitution to form halogenoalkanes, e.g. by reaction with HX(g); or with KCl and concentrated \( H_2SO_4 \) or concentrated \( H_3PO_4 \); or with PCl\(_3\) and heat; or with PCl\(_5\); or with SOCI\(_2\) (c) the reaction with Na(s) (d) oxidation with acidified \( K_2Cr_2O_7 \) or acidified KMnO\(_4\) to: (i) carbonyl compounds by distillation (ii) carboxylic acids by refluxing (primary alcohols give aldehydes which can be further oxidised to carboxylic acids, secondary alcohols give ketones, tertiary alcohols cannot be oxidised) (e) dehydration to an alkene, by using a heated catalyst, e.g. \( Al_2O_3 \) or a concentrated acid (f) formation of esters by reaction with carboxylic acids and concentrated \( H_2SO_4 \) as catalyst as exemplified by ethanol
describe: (a) the reduction of aldehydes and ketones using NaBH\(_4\) or LiAlH\(_4\) to produce alcohols (b) the reaction of aldehydes and ketones with HCN, KCN as catalyst, and heat to produce hydroxymitriles as exemplified by ethanol and propanone
