haloalkanes

Question 1

free radical substitution

Answer 1

UV light- provides energy required to break the halogen-halogen bond at the start of the reaction
Definition: A species with an unpaired electron
mechanism:
Initiation- Cl2–> 2Cl*
Propagation- Cl* + CH4 –> CH3 + HCl
CH3 + Cl2 –> CH3Cl + Cl
termination:
CH3 + *Cl –> CH3Cl
2CL –> Cl2
2CH3 –> CH3CH3
(two radicals combine)

Question 2

Curly arrow use

Answer 2

To shpw the movement of electrons

Question 3

Nucleophile definition

Answer 3

An electron-pair donor

Question 4

Strength of C=C bond

Answer 4

C=C bond is stronger than a single bond because it has more electrons. A pie bond is weaker than a sigma bond. A pie bond is more reactive. Allene is more reactive. Can’t react because the pie bond is formed by an overlap of p orbitals and this would be lost resulting in a break of bond.

Question 5

Definition of an electrophiles

Answer 5

Accepts a electron pair

Question 6

Major and minor products

Answer 6

X is made from a 2º carbocation whereas Y is made from a 1º carbocation. 2º is more stable due to a more positive inductive effect.

Question 7

Why does bromine react in electro Philip addition even though its a non-polar molecule

Answer 7

C=c is electron rich, this induces a dipole across the Br2 molecule. The d+ Br atom accepts an electron pair.

Question 8

Test for Alkenes

Answer 8

Bromine water
Allene= orange to colourless
Anything else-nvc
CH2=CH2 +Br2 —> CH2BrCH2Br

Question 9

Aldehyde

Answer 9

Structural formula: CHO
Ending: al
Carbonyl bonded to at least 1H atom

Question 10

Ketone

Answer 10

Carbonyl bonded to 2 carbon atoms
Structural formula: CO
Ending: one

Question 11

Carboxylic acid

Answer 11

Carbonyl bonded to an OH group
Ending: oic acid
Structural: COOH

Question 12

Oxidation of alcohols

Answer 12

Acidified K2Cr2H7 and conc sulfuric acid
Turns orange to green
Reagent. O used H20 produced. Product. Conditions
Primary alcohol. 1. 1. Aldehyde Distillation
Aldehyde. 1. 0. Carboxylic acid Reflux
Primary alcohol 2. 1. Carboxylic acid. Reflux
Secondary alcohol. 1. 1. Ketone. Reflux or distillation

Question 13

Oxidation statements

Answer 13

Features of condenser: open at both ends, cold water flows around outside
Purpose of condenser: cool hot vapour condenses it to a liquid
Anti bumping granules used to prevent formation of larger bubbles

Question 14

Test for aldehyde

Answer 14

Tollens: forms silver mirror
Equation: [Ag(NH3)2]+ +e- —> Ag (s) +2NH3
Fehling’s: forms brick red precipitate
Equation: Cu2+ +e- —> Cu+

Question 15

Test for Carboxylic acid

Answer 15

Na2CO3- forms effervescence
Equation: CO32- +2H+ —> CO2 + H20

Question 16

Primary alcohol –> aldehyde

Answer 16

K2Cr2O7, acidified with conc H2SO4, heat under distillation
CH3CH2OH + [O]–> CH3CHO + H2O

Question 17

Aldehyde –> Carboxylic acid

Answer 17

K2Cr2O7, acidified with conc H2SO4, heat under reflux
CH3CHO + [O]–> CH3COOH

Question 18

1º alcohol –> carboxyllic acid

Answer 18

K2Cr2O7, acidified and heat under reflux
CH3CH2OH + 2[O] –> CH3COOH + H20

Question 19

2º –> ketones

Answer 19

K2Cr2O7. acidified , heat under reflux or distillation
CH3CH9OH)CH3 + [O] –> CH3COCH3 + H2O
3º cant react because no hydrogens aren’t available on the carbon.

Question 20

Why is reflux used to oxidise a 1º alcohol to carboxyllic acid

Answer 20

To prevent any vapour escaping from the reaction mixture.

Question 21

hat happens to the aldehyde as it is produced during distillation

Answer 21

Aldehyde boils and vaporises, then escapes from the mixture.

Question 22

Ethanol can be oxidies to ethanal or ethanoic acid. describe how ethanal can be made in high yield, as opposed to ethanoic acid

Answer 22

heat mixture to boiling point of ethanal, set up distillation. maintain temp at boiling point so aldehyde is condensedto a liquid and collected.

Question 23

Why no rotation around double bond

Answer 23

The pie bond is formed by overla of p orbitals. if any rotation, p orbiyals would no longer overlap and pie bond would break.

Question 24

What is a positive inductive effect

Answer 24

The ability to release electron density through a covalent bond