4.2.1 alcohols

Question 1

what is the shape and bond angle around the O and why

Answer 1

bent 104.5° repulsion between two bond pairs and two lone pairs

Question 2

what intermolecular forces are involved in alcohols

Answer 2

permanent dipole, hydrogen bonding

Question 3

what properties does the hydrogen bonding cause in alcohols

Answer 3

• low volatility
• high m.p and b.p due to strong hydrogen bonding
• able to dissolve in water due to hydrogen bonds that can bond to water

Question 4

what happens when alcohols are combusted in excess oxygen

Answer 4

complete combustion

Question 5

in an oxidation reaction what is the reagent also called as

Answer 5

oxidising agent

Question 6

what is the reagent in oxidation reactions with alcohol

Answer 6

potassium dichromate K2Cr2O7

Question 7

what distils first and why aldehydes or alcohols

Answer 7

aldehydes as alcohols have hydrogen bonding whereas aldehydes have permanent dipole-dipole

Question 8

describe reflux condition

Answer 8

• continual evaporation and condensing of organic reagents
• end of the condenser is left open to prevent explosion from pressure build-up
• a water bath or electric heater is used as the organic reagent is flammable
• anti-bumping granules are used to prevent vigorous uneven boiling

Question 9

what is distillation used for

Answer 9

separating organic product from reagent

Question 10

what condition and reagent is needed to form an aldehyde from a primary alcohol in an oxidation reaction

Answer 10

distillation and k2cr2o7/h2so4

Question 11

what is the general equation when a primary alcohol forms an aldehyde in an oxidation reaction

Answer 11

ch3ch2oh + [o] —> rhco + h2o

Question 12

describe the identification test for primary alcohols

Answer 12

add k2cr2o7 observe a yellow to green colour change as dichromate ion (cr2o7-2) reduced to cr+3 ion the product is then distilled and tested with Tollen’s reagent observe a silver mirror

Question 13

what condition and reagent is needed to form a carboxylic acid from a primary alcohol in an oxidation reaction

Answer 13

reflux and k2cr2o7/h2so4

Question 14

what is the general equation when a primary alcohol forms a carboxylic acid in an oxidation reaction

Answer 14

rch2 + 2[o] —> rcooh + h2o

Question 15

describe the identification test for a carboxylic acid

Answer 15

add sodium carbonate Na2CO3 observe effervescence

Question 16

what condition and reagent is needed to form a ketone from a secondary alcohol in an oxidation reaction

Answer 16

reflux and k2cr2o7/h2so4

Question 17

what is the general equation when a secondary alcohol forms a ketone in an oxidation reaction

Answer 17

rchohr + [o] —> rcor + h2o

Question 18

describe the identification test for a secondary alcohol

Answer 18

add k2cr2o7 observe a yellow to green colour change as dichromate ion (cr2o7-2) reduced to cr+3 ion the product is then distilled and tested with Tollen’s reagent observe no change

Question 19

why can tertiary alcohols not undergo oxidation reactions

Answer 19

they are resistant because there is no h-c with the oh group, they can be combusted but will not react with k2cr2o7

Question 20

describe the identification test for a tertiary alcohol

Answer 20

add k2cr2o7/h2so4 no observational change

Question 21

why are anti bumping granules added when distilling and using reflux

Answer 21

prevent vigorous uneven boiling

Question 22

how is tollen’s reagent formed

Answer 22

mixing aqueous ammonia and silver nitrate to make [ag(nh3)2]+

Question 23

what is elimination / dehydration

Answer 23

the loss of an atom or group of atoms from a molecule

Question 24

what are the conditions and the reagent in elimination of alcohols

Answer 24

reflux and concentrated h2so4 or h3po4

Question 25

what is the general equation of an elimination reaction of alcohol

Answer 25

r2chr’2oh —> r2c=cr’2 + h2o