Alcohols

Question 1

what functional group does alcohol contain?

Answer 1

OH

Question 2

what are the boiling points of alcohol and why?

Answer 2

they have a higher than expected boiling point due to the strong hydrogen bonds between the molecules. They are much stronger than the induced dipole-dipole forces which are present between non-polar alkanes

Question 3

What about the solubility of alcohols?

Answer 3

Low molecular alcohols are extremely soluble in water due to the hydrogen bonds which can form between the water molecules and the alcohol molecules.

Question 4

as the length of the carbon chain increases

Answer 4

solubility decreases

Question 5

as the number of hydroxyl groups increase

Answer 5

solubility increases

Question 6

what colour do low-molecular alcohols burn?

Answer 6

burn smoothly with a blue or colourless flame, without a lot of smoke

Question 7

under conditions of a good supply of oxygen…

Answer 7

complete combustion takes place to form carbon dioxide and water.

Question 8

alcohol react with sodium

Answer 8

Sodium is a highly reactive metal which is able to displace the hydrogen atom from the hydroxyl group. The reaction is slower than that with water, as the O-H bond is stronger in the alcohol than in water, so is less easily broken.

Question 9

what does the reaction with sodium show?

Answer 9

The reaction shows the evolution of a gas which can be tested for, using a lit spill, producing the characteristic “squeaky pop” test for the presence of hydrogen gas.

Question 10

how is sodium disposed in terms of COSHH guidance?

Answer 10

Sodium is disposed of by placing small amounts in propan-2-ol
Once the reaction is complete, it is carefully added to water and poured down the foul-water drain

Question 11

what reagents are used with the oxidation with dichromate (VI)?

Answer 11

Potassium dichromate (VI); (oxidising agent) conc. Sulfuric Acid (K2Cr2O7 / H2SO4)

Question 12

what conditions are used with the oxidation with dichromate (VI)?

Answer 12

HEAT Depends upon the desired product. (Distillation or Reflux)

Question 13

what observations are seen with the oxidation with dichromate (VI)?

Answer 13

Orange to green solution

Question 14

what are primary alcohols first oxidised to?

Answer 14

an aldehyde, which contains the carbonyl functional group

Question 15

what can the aldehyde be further oxidised to?

Answer 15

to the carboxylic acid

Question 16

what is the overall reaction from primary alcohol to aldehyde?

Answer 16

R-CH2OH + [O] –> R-CHO + H2O

Question 17

what is the overall equation from primary alcohol to carboxylic acid?

Answer 17

R-CH2OH + 2[O] –> R-COOH + H2O

Question 18

if you start with an alcohol in oxidation what is aways produced?

Answer 18

water

Question 19

what conditions are used to favour an aldehyde?

Answer 19

continuous distillation

Question 20

how does distillation work to favour an aldehyde?

Answer 20

Distillation removes the aldehyde from the oxidising agent to prevent further oxidation to the carboxylic acid.
The aldehyde can be removed/ separated by distillation as it has a lower boiling point than the alcohol.

Question 21

how do you favour the carboxylic acid?

Answer 21

heat using reflux and an excess of acidified potassium dichromate

Question 22

what is an alternative for Oxidation of Primary Alcohols (forming aldehydes / carboxylic acids)?

Answer 22

Alternatively, you could start with an aldehyde and oxidised it to a carboxylic acid

Question 23

if you start with an aldehyde, what products are produced?

Answer 23

the carboxylic acid is the only product. Water is not produced

Question 24

oxidation of secondary alcohols

Answer 24

Secondary alcohols can be oxidised to the ketone, but cannot be further oxidised as there is only one hydrogen directly attached to the alcohol group.

Question 25

what reagents are used with the oxidation of secondary alcohols?

Answer 25

Potassium dichromate, sulfuric acid

Question 26

what conditions are used with the oxidation of secondary alcohols?

Answer 26

Heat and Reflux

Question 27

what is the equation for the oxidation of secondary alcohols?

Answer 27

R2CHOH + [O] --> RCOR + H2O

Question 28

what is the observation in the oxidation of secondary alcohols?

Answer 28

The oxidising agent again changes colour from orange to green exactly the same as for a primary alcohol.

Question 29

what is different about tertiary alcohols?

Answer 29

Tertiary alcohols can't be oxidised as they have no hydrogens directly attached to the carbon of the alcohol group, so there are none to remove. The colour remains orange.

Question 30

how does reflux - aldehyde reactions work?

Answer 30

the aldehyde is heated until it forms the carboxylic acid but the water jacket condenser prevents the aldehyde escaping as vapour. Vapour has a lower bp than the carboxylic acid

Question 31

what is distillation used for?

Answer 31

as a separation technique to separate an organic product from its reacting mixture. need to collect the distillate of the approximate boiling point range of the desired liquid

Question 32

what reagents are used for the substitution with hydrogen halides?

Answer 32

sodium halide, conc sulfuric acid

Question 33

what conditions are used for the substitution with hydrogen halides?

Answer 33

heat and reflux

Question 34

What is the equation for the hydrogen halide substitution?

Answer 34

The sodium halide and sulfuric acid react together to form the hydrogen halide, HX. NaX + H2SO4 --> HX + NaHSO4

Question 35

what does the hydrogen halide react with and form?

Answer 35

reacts with an alcohol in a substitution reaction to produce a haloalkane

Question 36

what is the reaction mechanism?

Answer 36

nucleophilic substitution

Question 37

what is the first step of nucleophilic substitution?

Answer 37

The first step is protonation from the acid.

Question 38

what does protonation from the acid do?

Answer 38

This weakens the bond between the carbon and oxygen, so it breaks more easily and produces a good leaving group (H2O+), so the carbon becomes more susceptible to attack by the nucleophile.

Question 39

if the alcohol molecule is unsymmetrical and the OH group is not on the end chain, what happens?

Answer 39

it will dehydrate to form a mixture of two products – which are structural isomers.

Question 40

what are the reagents used for esterification?

Answer 40

carboxylic acid, conc sulfuric acid (catalyst)

Question 41

what are the conditions used for esterification?

Answer 41

heat and reflux followed by distillation

Question 42

what is the equation for esterification?

Answer 42

R-CH2OH + R2-COOH ⇌ R2-COOCH2-R + H2O

Question 43

in naming esters, how does this happen?

Answer 43

alcohol named first and then carboxylic named last

Question 44

what reaction is esterification?

Answer 44

equilibrium

Question 45

how do you improve the yield in esterification?

Answer 45

To improve the yield, the process is first heated under reflux to obtain the equilibrium and the ester product is then distilled off.

Question 46

what boiling point does the ester have and why?

Answer 46

The ester has a lower boiling point due to the weaker intermolecular forces than either of the reactants

Question 47

what does removing the products do to equilibrium?

Answer 47

Removing the product shifts the equilibrium further to the right-hand side so more ester is produced.

Question 48

how can esters be produced more efficiently?

Answer 48

using acyl chlorides, where the reaction goes to completion.

Question 49

why do acyl chlorides cause better completion?

Answer 49

The acyl chloride has a weaker bond and is much more reactive than the carboxylic acid.

Question 50

what condition must the acyl chloride reaction be kept and why?

Answer 50

The acyl chloride reaction must be kept dry, as the acyl chloride is very easily hydrolysed.

Question 51

what class of alcohol is menthol

Answer 51

secondary

Question 52

what alcohol solubility is menthol?

Answer 52

Only slightly due to presence of large number of C’s

Question 53

what is the molecular formula of menthol?

Answer 53

C10H20O

Question 54

what is the balanced equation for complete combustion of menthol?

Answer 54

C10H20O + 14½O2 → 10CO2+ 10H2O

Question 55

what is the reaction and mechanism to form alkenes?

Answer 55

reaction - dehydration mechanism - elimination

Question 56

what reagents are needed for elimination?

Answer 56

conc sulfuric acid

Question 57

what conditions are needed for elimination?

Answer 57

170oC Heat and reflux

Question 58

what equation is used for dehydration/elimination?

Answer 58

CH3CH2OH --> CH2=CH2 + H2O

Question 59

what is concentrated sulfuric acid and how?

Answer 59

Concentrated Sulfuric acid is a dehydrating agent. It has a great affinity for water and the elements of water and is able to remove water easily from molecules.