ALCOHOLS

Question 1

General formula of alcohols

Answer 1

CnH2n+1OH

Question 2

shape of alcohols

Answer 2

oxygen atom has two bonding pairs and two lone pairs
C-O-H bond is about 105 degrees
lone pairs repel each other more than bonded pairs

Question 3

what 3 ways can alcohols be categorised

Answer 3

primary
secondary
tertiary

Question 4

alcohol boiling point

Answer 4

greater than alkanes with a similar mr
alkanes only have VDW forces between molecules
alcohols have VDW forces and hydrogen bonding between molecules
hydrogen bonding is a stronger IMF than VDW forces therefore requires more energy to overcome

Question 5

solubility of alcohols

Answer 5

OH group can form hydrogen bonds with water molecules
small alcohol molecules are very soluble in water. as chain length increases solubility decreases
for longer chains, the non polar VDW forces dominate and solubility decreases

Question 6

volatility of alcohols

Answer 6

relatively low volatility due to having high boiling points

Question 7

uses of alcohols

Answer 7

fuels
solvents
alcoholic drinks

Question 8

two ways ethanol can be produced

Answer 8

hydration of ethene
fermentation

Question 9

what is hydration

Answer 9

addition of water to a molecule

Question 10

hydration of ethene

Answer 10

reagent - excess steam
catalyst- concentrated phosphoric acid
conditions - 300 degrees, 6oatm and excess steam
mechanism - electrophilic addition
H+ from acid acts as an electrophile- attracted to electron dense area
double bond will break and we will form a carbocation
oxygen in steam has 2 lone pairs of electrons
acts as a nucleophile and will form a bond with the carbocation
oxygen has a slightly positive charge when it forms that bond so the O-H bond breaks
ethanol is produced and catalyst is regenerated at the end

Question 11

fermentation

Answer 11

carbs from plants are broken down into sugars
then converted into ethanol by the action of enzymes from yeast

Question 12

why are anaerobic conditions used during fermentation

Answer 12

oxygen from air is kept out to prevent oxidation of ethanol to ethanoic acid

Question 13

advantage of carrying fermentation out at higher temps

Answer 13

ethanol is produced at a faster rate

Question 14

disadvantage of carrying out fermentation at high temps`

Answer 14

more energy is used

Question 15

how is pure ethanol obtained from industrial fermentation

Answer 15

fractional distillation to separate water and ethanol as they have different boiling points

Question 16

hydration vs fermentation process

Answer 16

fermentation - batch process. reactants are placed in a container until fermentation is complete. this is then cleared out and a new reaction is set up. VERY INEFFICIENT
hydration of ethene - a continuous flow process with automation. MORE EFFICIENT

Question 17

hydration vs fermentation rate of reaction

Answer 17

fermentation - very slow
hydration - very fast

Question 18

fermentation vs hydration quality of product

Answer 18

fermentation - impure ethanol
hydration - pure ethanol

Question 19

hydration vs fermentation reaction conditions

Answer 19

fermentation- low temp and pressure
hydration - high temp and pressure so lots of energy needed

Question 20

hydration vs fermentation use of resources

Answer 20

fermentation - renewable resources from plants
hydration - finite resources from crude oil