Alcohols, haloalkanes and analysis

Question 1

What is a primary alcohol?

Answer 1

The OH is bonded to a carbon atom that has a bond to one other carbon atom

Question 2

What is a secondary alcohol?

Answer 2

The OH is bonded to a carbon atom that has a bond to two other carbon atoms

Question 3

What is a tertiary alcohol?

Answer 3

The OH is bonded to a carbon atom that has a bond to three other carbon atoms

Question 4

Why do alcohols have relatively low volatility compared to alkanes?

Answer 4

Ethanol forms H bonds, which are stronger than London forces alone so the b.p. of alcohols are higher than akanes

Question 5

What is volatility?

Answer 5

The ease that a liquid turns to a gas

Question 6

Why are alcohols soluble in water?

Answer 6

They are polar molecules as the OH group gives it a slightly negative and positive charge, therefore it can form hydrogen bonds within the water and dissolve

Question 7

What is the balanced equation for the incomplete combustion of ethanol?

Answer 7

C2H5OH + 2O2 → 2CO + 3H2O

Question 8

What does oxidation of primary alcohols produce?

Answer 8

Aldehydes then carboxylic acid

Question 9

What does the oxidation of secondary alcohols produce?

Answer 9

Ketone

Question 10

What does the oxidation of tertiary alcohols produce?

Answer 10

Cannot be oxidised

Question 11

What is the reagent and conditions for the formation of aldehydes from primary alcohols?

Answer 11

K2Cr2O7/ Dil. H2SO4
Heat and distillation

Question 12

What is the equation for the oxidation of ethanol to ethanal?

Answer 12

C-C-OH + [O] = C-C=O (-H)+ H20

Question 13

Why is distillation appropriate for the oxidation of primary alcohols to aldehydes?

Answer 13

Aldehydes don’t form hydrogen bonds like alcohols, therefore they have a lower boiling point

Question 14

What is the colour change in the oxidation of alcohols?

Answer 14

Orange to green

Question 15

What gives the solution of alcohols for oxidation their colour?

Answer 15

Orange is caused by dichromate and the final green is caused by the chromium ions

Question 16

What are the reagents and conditions for the formation of carboxylic acids from primary alcohols?

Answer 16

K2Cr2O7/ Dil. H2SO4
Heat + reflux

Question 17

What is the balanced equation for the formation of ethanoic acid from ethanol

Answer 17

C-C-OH + 2[O] = C-C=O(-OH) +H2O

Question 18

What is the reagents for the formation of ketones from secondary alcohols?

Answer 18

K2Cr2O7/ Dil. H2SO4
Heat + reflux

Question 19

What is the equation for the oxidation of propan-2-ol to propanone

Answer 19

C-C(OH)-C + [O] = C-C(=O)-C + H2O

Question 20

Why is reflux appropriate for oxidation of secondary alcohols?

Answer 20

Ketones do not undergo further controlled oxidation, so reflux will only ensure that all of the alcohol has been oxidised

Question 21

Why aren’t tertiary alcohols oxidised?

Answer 21

They do not contain a hydrogen atom on the carbon atom that the OH group os attached to

Question 22

What are the reagents and conditions for dehydration of alcohol?

Answer 22

Conc. H2SO4 (catalyst)
Heat + reflux

Question 23

What is the equation for the dehydration of ethanol?

Answer 23

C2H5OH = C2H4 + H2O

Question 24

What happens when secondary alcohols are dehydrated?

Answer 24

A mixture of alkenes can be formed

Question 25

What happens when butan-2-ol is dehydrated?

Answer 25

Formation of but-1-ene or but-2-ene (E/Z isomers)

Question 26

What are the reagents and conditions needed for the production of haloalkanes from alcohols?

Answer 26

Alcohol, NaX, conc. H2SO4
Heat + reflux

Question 27

What is the overall equation for the formation of bromopropane from propanol?

Answer 27

NaBr + H2SO4 + C3H7OH = NaHSO4 + C3H7Br + H2O

Question 28

Why are there two equations for the formation of haloalkanes?

Answer 28

The hydrogen halide must be formed first

Question 29

What are nucleophilic substitution reactions in haloalkanes?

Answer 29

When the atom or group replacing halogen possess a lone pair of electrons

Question 30

What are the reagents and conditions for the hydrolysis of haloalkanes by aqueous alkali?

Answer 30

Reagents: haloalkane dissolved in ethanol
Conditions: Dil aq NaOH, heat + reflux

Question 31

What is the equation for the hydrolysis of iodomethane?

Answer 31

H3C-I + OH- = H3C-OH + I-

Question 32

What’s the mechanisms for nucleophilic substitution in hydrolysis of primary haloalkanes with aqueous alkali?

Answer 32

The halogens are more electronegative than carbon so pull the electron pair so the nucleophile can easily replace halogens and form a halide ion

Question 33

What is formed when primary haloalkanes react with water?

Answer 33

Alcohol and hydrogen halide

Question 34

What is the trend for the rate of hydrolysis in haloalkanes?

Answer 34

Moving from fluorine to iodine it becomes faster as the bond energy decreases

Question 35

How can the rate of reaction be determined in hydrolysis of primary haloalkanes?

Answer 35

Adding silver nitrate solution and measure the rate at which precipitate forms, iodine is the fastest and chlorine the slowest

Question 36

How many molecules of O3 can one chlorine radical destroy?

Answer 36

100,000

Question 37

What type of reaction do alkenes undergo?

Answer 37

Electerophillic addition

Question 38

What type of reaction do alkanes undergo?

Answer 38

Radical substitution

Question 39

What type of reactions do alcohols undergo?

Answer 39

Nucleophillic substitution, elimination or dehydration

Question 40

What type of reaction do haloalkanes undergo?

Answer 40

Nucleophillic substitution