Alcohols

Question 1

General formula of alcohols

Answer 1

CnH2n+1OH

Question 2

Polygydric alcohols

Answer 2

Alcohols containing more than one OH group

Question 3

bp off alcohols in relation to alkanes 2

Answer 3

Higher than alkanes with the same number of C atoms (and les ls volatile)
Difference in bp decreases as chain length increases

Question 4

In relation to intermolecular forces, why do alkanes have lower bp than alcohols

Answer 4

Alkanes: Non polar molecules so weaker London forces between molecules
Alcohols: Polar molecules, form stronger H bonds between molecules
Difference in energy req to overcome forces

Question 5

Solubility in water of alcohols vs alkanes, why

Answer 5

Alcohols are more soluble in water bc the -OH forms H bonds to water molecules

Question 6

Why and how does solubility of alcohols change as chain length increases 3

Answer 6

Hydrocarbon chain is non polar
So cannot form H bonds with water molecules
So solubility of alcohols decreases as chain length increases (only small chain are soluble)

Question 7

How does viscosity of alcohols change as number of OH groups increase, why

Answer 7

Viscosity increases bc more H bonds can form between molecules, req more energy to overcome

Question 8

Primary alcohol

Answer 8

The OH carbon is directly bonded to only one other carbon/ had 2 H

Question 9

Secondary alcohol

Answer 9

The OH carbon is bonded directly to 2 othe Cs/ has 1 H

Question 10

Tertiary alcohol

Answer 10

The OH carbon is has 3 other carbons bonded/ no H

Question 11

Why do alcohols undergo complete combustion with less O2 than alkanes

Answer 11

Bc they already have an O in their formula

Question 12

What state are small chain alcohols, benefit?

Answer 12

Liquid, makes them easily transportable so good fuels

Question 13

Reflux? when is it used

Answer 13

Method of continuous heating of volatile reactants without any loss
Used when taking reactions to completion

Question 14

Reflux?

Question 15

Distillation (distill)

Answer 15

Means of separating liquids based on their boiling points

Question 16

Dehydration reaction?

Answer 16

Water molecule is removed from the starting material (elimination)

Question 17

Process/ conditions of dehydration of alcohols

Answer 17

Heat under reflux in the presence of an acid catalyst

Question 18

Acid catalysts that can be used in reflux?

Answer 18

Concentrated phosphoric or sulfuric acid

Question 19

Reactants in the substitution of the OH in alcohols

Answer 19

NaBr, H2SO4, Alcohol

Question 20

Products of ‘side reaction’ of NaBr and H2SO4 in overall substitution reaction of alcohols

Answer 20

HBr is formed in situ (goes on to react with the alcohol)
NaHSO4 (does not partake in substitution)

Question 21

Condition req in substitution of alcohols

Answer 21

Reflux

Question 22

Is benzene with -OH group an alcohol

Answer 22

No, it’s a phenol

Question 23

What type of condenser does reflux use vs distillation

Answer 23

Vertical vs side mouthed

Question 24

What are the products of dehydration of alcohols

Answer 24

Alkene and water

Question 25

Final products if substitution of alcohols

Answer 25

Haloalkane, water, sodium hydrogen sulfate

Question 26

Oxidizing agent in the oxidation of alcohols

Answer 26

Acidified (by sulfuric acid) dichromate ions: H+/Cr2O7-

Question 27

Explain and give the colour change of dichromate ions

Answer 27

As an oxidizing agent, the orange Dichromate (VI) ions themselves are reduced to Chromium (III) ions which are green

Question 28

Conditions and products of incomplete oxidation of 1° alcohols

Answer 28

Distill, [O], Alderhyde, water

Question 29

Conditions and products of complete oxidation of 2°

Answer 29

Reflux, [O] Carboxylic acids, water

Question 30

Conditions and products of complete oxidation of 2°

Answer 30

Reflux, [O] ketone, water

Question 31

Can 3° be oxidised, why

Answer 31

No, in oxidation another H from the C bound to the OH group should be donated, 3° do not have any H bound to the OH carbon

Question 32

FG of alderhydes and suffix

Answer 32

-COH -al

Question 33

FG of ketones and suffix

Answer 33

-CO -one

Question 34

What is the name of the group ketones and alderhydes have in common

Answer 34

carbonyl Ketones is found in middle of chain Alderhydes must be at end of chain

Question 35

How are molecules containing a hydroxyl group and other groups of higher priority named

Answer 35

Prefix hydroxy- is used

Question 36

Oxidation vs Reduction regarding organic compounds

Answer 36

Oxidation is loss of H, gain of O Reduction is gain of H, loss of O