A-LEVEL CHEMISTRY: 3.3.5: Alcohols (ChemRevise)

Question 1

if the compound has an -OH group in addition to other functional groups that need a suffix ending then the OH can be named with the prefix…

Answer 1

hydroxy-

Question 2

if there are 2 or more -OH groups, then…

Answer 2

di, tri, are used

Question 3

alcohols have relatively ___ volatility and ___ bp. why?

Answer 3

low, high.
due to their ability to form strong hydrogen bond between alcohol molecules

Question 4

smaller alcohols can ___ in water. why?

Answer 4

dissolve. because they can form hydrogen bonds to water molecules

Question 5

primary alcohols:

Answer 5

primary alcohols are alcohols where 1 carbon is attached to the carbon adjoining the oxygen

Question 6

secondary alcohols:

Answer 6

secondary alcohols are alcohols where 2 carbons are attached to the carbon adjoining the oxygen

Question 7

tertiary alcohols:

Answer 7

tertiary alcohols are alcohols where 3 carbon are attached to the carbon adjoining the oxygen

Question 8

Potassium dichromate, ___, is an ___ ___ that causes ___ to ___.

Answer 8

K2Cr2O7, oxidising agent, alcohols, oxidise

Question 9

explain partial oxidation of primary alcohols: (3)

Answer 9

-reaction: primary alcohol —> aldehyde

-reagent: potassium dichromate (VI) solution and dilute sulfuric acid

-conditions: warm, gently distil out the aldehyde as it forms

Question 10

aldyhyde name ends in…

Answer 10

-al

Question 11

explain full oxidation of primary alcohols: (3)

Answer 11

-reaction: primary alcohol —> carboxylic acid

-reagent: potassium dichromate (VI) solution and dilute sulfuric acid

-conditions: excess of potassium dichromate, heat under reflux

Question 12

reflux:

Answer 12

reflux is used when heating organic reaction mixtures for specific periods of time, while continually cooling the vapour produced back into liquid form, using a condenser

Question 13

when refluxing: (2)

Answer 13

-never seal the end of the container (due to build up of gas)

-anti-bumping granules (form small bubbles instead of large bubbles)

Question 14

___ alcohols cannot be ___ at all by potassium dichromate. why?

Answer 14

tertiary, oxidised

because there is no hydrogen atom bonded to the carbon with the -OH group

Question 15

explain oxidation of secondary alcohols: (3)

Answer 15

-reaction: secondary alcohol —> ketone

-reagent: potassium dichromate(VI) solution & dilute sulfuric acid

-conditions: heat under reflux

Question 16

how to distinguish between aldehydes and ketones:

Answer 16

Tollens’ Reagent and Fehling’s Solution

Question 17

test for the presence of carboxylic acid:

Answer 17

addition of sodium carbonate. it will fizz & produce carbon dioxide if present

Question 18

explain reaction of alcohols with dehydrating agents: (4)

Answer 18

-reaction: alcohol —> alkene

-reagents: concentrated sulfuric or phosphoric acids

-conditions: warm (under reflux)

-role of reagent: dehydrating agent/catalyst

-type of reaction: acid catalysed elimination

Question 19

dehydration reaction:

Answer 19

removal of a water molecule from a molecule

Question 20

2 methods for forming ethanol: (2)

Answer 20

-fermentation

-industrial (from ethene)

Question 21

word equation for formation of ethanol from fermentation:

Answer 21

glucose —> ethanol + carbon dioxide

Question 22

symbol equation for formation of ethanol from fermentation:

Answer 22

C6H1206 —> 2CH3CH2OH + 2CO2

Question 23

conditions needed for formation of ethanol from fermentation: (3)

Answer 23

-yeast

-no air

-temperatures (30’C - 40’C)

Question 24

type of reaction of formation of ethanol from fermentation:

Answer 24

fermentation

Question 25

optimum temperature for formation of ethanol from fermentation: why?

Answer 25

~38'C at lower temp., reaction is too slow at higher temp., the yeast dies & the enzymes denature

Question 26

fermentation is done in the absence of ___. why?

Answer 26

air. because the presence of air can cause extra reactions to occur

Question 27

advantages of formation of ethanol from fermentation: (2)

Answer 27

-sugar is a renewable resource -production uses low level technology/cheap equipment

Question 28

disadvantages of formation of ethanol from fermentation: (3)

Answer 28

-batch process (slow & high production costs) -ethanol made needs to be purified by fractional distillation -depletes land used for growing food crops

Question 29

reagent for industrial formation of ethanol is... where does it come from?

Answer 29

ethene from cracking of fractions from distilled crude oil

Question 30

type of reaction for industrial formation of ethanol?

Answer 30

hydration/addition

Question 31

essential conditions for industrial formation of ethanol: (3)

Answer 31

-high temperature -high pressure -strong acidic catalyst H3PO4

Question 32

advantages of industrial formation of ethanol: (3)

Answer 32

-faster reaction -product formed is pure -continuous process (cheaper manpower)

Question 33

disadvantages of industrial formation of ethanol: (3)

Answer 33

-expensive equipment -ethene is non-renewable (ethene is the reagent used) -high energy costs (for high temp. & pressure)

Question 34

biofuel:

Answer 34

a biofuel is a fuel produced from plants

Question 35

carbon neutral:

Answer 35

an activity that has no net annual carbon emissions to the atmosphere

Question 36

ethanol produced from fermentation is a ___.

Answer 36

biofuel

Question 37

ethanol produced from ___ is a biofuel

Answer 37

fermentation