2.7 Alcohols and Carboxylic acids

Question 1

what is alcohol?

Answer 1

alcohol is a homologous series containing OH as the functional group

Question 2

summarise the industrial preparation of ethanol

Answer 2

reagents and conditions: H2O(steam), H3PO4, 3oo*C, 60atm
mechanism: electrophilic addition
gen equation: C2H4 + H2O ⇋ CH3CH2OH

Question 3

describe the temperature in the industrial preparation of ethanol

Answer 3

forward reaction, so exothermic therefore produces a high yield favoured by a low temp. However, this equals a slower rate of reaction so 300*C compromise

Question 4

describe the pressure in the industrial preparation of ethanol

Answer 4

2 mols of gaseous reactants give 1 mol of gaseous product therefore high yield favoured by higher pressyre, also rate of reaction increases but too high pressure is costly

Question 5

describe the catalyst in the industrial preparation of ethanol

Answer 5

rate of reaction increases without affecting yield

Question 6

What’s another way to make ethanol? Describe/summarise this process

Answer 6

Fermentation.
reagents: C6H12O6, yeast catalyst, room temp and press
gen equation: C6H12O6 -> 2C2H5OH + 2CO2

Question 7

what is ethanols boiling temp and how is it separated?

Answer 7

80*C
to be separated it’s left in fermentation vessel by fractional distillation

Question 8

What are biofuels? How is bioethanol obtained? Biodiesel?

Answer 8

made from living organisms
bioethanol obtained by fermentation of sugars in plants
biodiesel from oils and fats present in seeds of some plants

Question 9

what are some advantages of biofuels?

Answer 9

renewable, can be regrown each year
greenhouse gases- do produce CO2 but plants by which they were formed take in CO2 during photosynthesis therefore carbon neutral
economic and political security, countries without own source of fossil fuels are affected by change in price

Question 10

what are some disadvantages of biofuels?

Answer 10

land use, deforestation, land used for biofuels cannot produce food crops
use of resources, large quantities of water and fertiliser needed
carbon neutrality? doesn’t account for the fuel needed to build factories and transport raw materials

Question 11

How do you make alcohols?

Answer 11

reagents - halogenoalkane + NaOH, heat under reflux
mechanism - nucleophilic substitution

Question 12

what is the dehydrogenation of alcohols the reverse of?

Answer 12

reverse of reaction of alkenes with steam

Question 13

What is the dehydrogenation of alcohols and summarise it

Answer 13

water removed (H from 1C and OH from next) and a double bond formed reagents - H2SO4 conc, heat under reflux
mechanism - elimination reaction
gen equation - C2H5OH -> C2H4 + H2O

Question 14

How do you distinguish primary alcohols from secondary and tertiary?

Answer 14

Primary - if OH joined to C that is itself joined to not more than 1 other C atom
Secondary - if OH joined to C that itself is joined to 2 other C atoms
Tertiary - if OH joined to C that is itself joined to 3 other C atoms

Question 15

How do you oxidise alcohols? what is an oxidising agent usually shown as? what is the colour change?

Answer 15

oxidising agent: acidified potassium dichromate (H+/Cl2O72-)
shown as [O]
colour change from orange-green

Question 16

What is the stage process of oxidising primary alcohols, eg propan-1-ol? what is lost? what s formed? draw in book

Answer 16

propan-1-ol + [O] -> propanal
propanal +[O] -> propanoic acid
2 H lost, 1 from OH, 1 from C
first aldehyde formed, then carboxylic acid

Question 17

What is the 1 stage process of oxidising secondary alcohols, eg propan-2-ol? what s formed? draw in book

Answer 17

propan-2-ol + [O] -> propanone
ketone formed

Question 18

what is the process of making tertiary alcohols?

Answer 18

tertiary not generally oxidised as no H on adjacent C that can be lost

Question 19

summarise the process of oxidising the three alcohols

Answer 19

primary - aldehydes - carboxylic acids
secondary - ketones
tertiary - not oxidised

Question 20

what are carboxylic acids? eg

Answer 20

weak acids so only partially dissociate to produce H+ ions
CH3COOH ⇋ CH3COO- + H+

Question 21

what are dimers? draw it

Answer 21

carboxylic acids are able to H-bond with themselves to create dimers

Question 22

how do carboxylic acids behave?

Answer 22

as acids, hey behave in the same way as strong inorganic aids when they react with bases, carbonates and hydrogencarbonates to form salts

Question 23

If carboxylic acids work the same way as strong inorganic acids, give some examples.

Answer 23

Acid + base -> salt + water
Acid + alkali -> salt + water Acid + carbonate -> salt + water + CO2
Acid + hydrogencarbonate -> salt + water + CO2

Question 24

What are esters?

Answer 24

organic compounds formed from an acid

Question 25

summrise the esterification of alcohols how can esters be separated? what are esters recognised by?

Answer 25

gen equation - acid + alcohol ⇋ ester + water catalyst - conc sulfuric acid ester can be separated by fractional distillation recognised by sweet, fruity odours

Question 26

give the equation of the esterification of ethanoic acid

Answer 26

ethanoic acid + ethanol -> ethyl ethanoate CH3COOH + C2H5OH -> CH3COOC2H5 + H2O

Question 27

compare the reactivity between alkanes and alkenes

Answer 27

both contain C-H and C-H has smiliar electronegativities no dipoles in either alkanes or alkenes alkenes have double bonds so more reactive due to high electron deficiency of the pi bond causes by p-p sideways overlap alkanes are saturated, alkenes unsaturated and therefore alkenes are more susceptible to electrophilic addition