Alcohols

Question 1

boiling point and solubility of alcohols

Answer 1

•boiling point:
- higher than similar molecular mass alkenes due to the prevents of H bonding
-higher for straight chain molecules (greater degree of branching = fewer intermolecular forces)
•solubility:
-less miscible as they get heavier
-alcohols themselves are very good solvents that dissolve a large number of organic molecules

Question 2

what are the two reagents that can break the OH bond of alcohols?

Answer 2

sodium or carboxylic acids

Question 3

explain the reaction of alcohols with sodium

Answer 3

• produces an alkoxide (eg. CH3CH2O-Na+) + H2

* reactivity with sodium decreases as the hydrocarbon chain gets longer

Question 4

explain the reaction of alcohols with carboxylic acids

Answer 4

• breaks the OH bond
• produces ester + water, impure ester is obtained by distillation
• concentrates sulfuric acid catalyst(DEHYDRATING AGNET), refluxed
• condensation reaction

Question 5

how can the C-O bond be broken?

Answer 5

substitution to form haloalkanes-reverse hydrolysis of haloalkanes

Question 6

***how are bromoalkanes, chloroalkanes and iodoalkanes formed by alcohols? (reagents + conditions)

Answer 6

• bromoalkanes: concentrated sulfuric acid and sodium/potassium bromide heated at reflux to form bromoalkane + water
• chloroalkanes: SOCl2 (room temp), PCl5 (room temp) or PCl3 (reflux)
• iodoalkanes: reflux red phosphorus and iodine to from iodoalkane + P(OH)3

Question 7

what are the two ways the C-H bond can be broken?

Answer 7

oxidation to form aldehydes/ketones, elimination/dehydration to form alkenes

Question 8

explain the oxidation of alcohols (reagent, conditions, products, 1° 2° 3°)

Answer 8

•1° alcohols:
-oxidised to aldehydes, important to DISTILL BEFORE it gets oxidised to carb. acid
-alcohol slowly added to warm solution of acidified K2Cr2O7, orange to green
•2° alcohols:
-oxidised to ketones
-refluxed with acidified K2Cr2O7
•3° alcohols: can’t be oxidised bc to oxidise there must be 2 H atoms on adjacent C and O atoms

Question 9

explain the elimination/dehydration of alcohols (reagent, conditions, product)

Answer 9

• alkene produced
• LAB = conc. H2SO4/H3PO4 + alcohol, heated at reflux
• INDUSTRY = vapour passed over hot powdered Al2O3

Question 10

how can the C-C bond be broken?

Answer 10

by oxidation, burning in oxygen to produce CO2 and water

Question 11

how can alcohols be prepared?

Answer 11

• haloalkanes

* alkenes