Alcohols

Question 1

General formula

Answer 1

CnH2n+1OH

Question 2

Primary, secondary, tertiary

Answer 2

1) ROH, 1 alkyl group 2) R2CHOH, 2 alkyl groups 3) R3COH, 3 alkyl groups

Question 3

Complete combustion (ethanol)

Answer 3

Products: CO2 and H2O

C2H5OH + 3O2 -> 2CO2 + 3H2O

Question 4

Halogenation: Chlorination

Answer 4

Phosphorus (V) chloride at room temp. (v. vigorous). Phosphorus oxychloride and hydrogen chloride as inorganic products.
Equation for reaction (w/ propan-1-ol):
CH3CH2CH2OH + PCl5 -> CH3CH2CH2Cl + POCl3 + HCl

Question 5

Chlorination of tertiary alcohols

Answer 5

Alcohol mixed w/ conc. HCl at room temp. Equation for reaction w/ 2-methylpropan-2-ol:
(CH3)3COH + HCl -> (CH3)3 CCl + H2O

Question 6

Halogenation: Bromination

Answer 6

50:50 potassium bromide and conc. sulfuric acid. Reaction mixture warmed w/ alcohol. 2 equations, inorganic reagents react together to form hydrogen bromide:
KBr + H2SO5 -> KHSO4 + HBr
2KBr + H2SO4 -> K2SO4 + 2HBr

Question 7

Halogenation: Iodination

Answer 7

Mixture of red phosphorus and iodine. Reaction mixture + alcohol heated under reflux. Two equations better, inorganic reagents react first (form phosphorus (III) iodide).
2P + 3I2 -> 2PI3
Reaction with ethanol:
3C2H5OH + PI3 -> 3C2H5I + H3PO3

Question 8

Dehydration to alkenes

Answer 8

Alcohol heated w/ conc. phosphorus acid. Several possible products, because C=C bond can go between different carbon atoms.
With butan-2-ol: CH3CH(OH)CH2CH3 -> CH2=CHCH2CH3 + H2O
OR  CH3CH(OH)CH2CH3 -> CH3CH=CHCH3 + H2O

Question 9

Oxidation of primary alcohols

Answer 9

Can be oxidised twice: aldehyde (RCHO), then carboxylic acid (RCOOH). Example reaction w/ propan-1-ol:
CH3CH2CH2OH + [O] -> CH3CH2CHO + H2O
CH3CH(OH)CH3 + [O] -> CH3COCH3 + H2O

Question 10

Oxidation of secondary alcohols

Answer 10

Ketone produced (RCOR). Example reaction w/ propan-2-ol:
CH3CH(OH)CH3 + [O] -> CH3COCH3 + H2O

Question 11

Usual reagent for oxidation reactions

Answer 11

Mixture of potassium dichromate (VI) and dilute sulfuric acid. Colour change from orange to green when oxidation has occurred.

Question 12

Obtaining a ketone or carboxylic acid

Answer 12

Heating under reflux. Products of oxidation stay in reaction mixture until they are completely oxidised.

Question 13

Incomplete oxidation technique

Answer 13

Aldehyde formed. Distillation with addition, only oxidising agent heated, alcohol added slowly.