Organic Chemistry I

Question 1

Which alcohols make carboxylic acids when oxidised?

Answer 1

Primary Alcohols

Question 2

Which alcohols make ketones when oxidised?

Answer 2

Secondary Alcohols

Question 3

What 4 reactions can alcohols do?

Answer 3

Combustion
Halogenation
Oxidation
Elimination

Question 4

Describe the solubility of alcohols.

Answer 4

• alcohols are miscible in water because of the O-H group
• this depends on the length of the non-polar part of the hydrocarbon
• however longer hydrocarbon chains decrease solubility as they cannot hydrogen bond with water

Question 5

What is a primary, secondary, and tertiary alcohol?

Answer 5

• primary alcohols are bonded to a carbon that is bonded to 1 other carbon
• secondary alcohols are bonded to a carbon that is bonded to 2 other carbons
• tertiary alcohols are bonded to a carbon that is bonded to 3 other carbons

Question 6

What happens in the combustion of alcohols?

Answer 6

Alcohols burn to produce CO2 and H2O (if its complete)

Question 7

What happens in chlorination of alcohols?

Answer 7

PCl5 is added to the alcohol, where any OH’s will be replaced by Cl.
e.g. PCl5 + C2H5OH -> C2H5Cl + POCl3 + HCl

• the POCl3 must be separated from the product using fractional distillation and the HCl will produce misty fumes

Question 8

What conditions must chlorination take place under?

Answer 8

• with dry ether (anhydrous conditions)
• because PCl5 will react with water

Question 9

Are primary or tertiary alcohols easier to chlorinate and why? (visualise)

Answer 9

• tertiary are easier
• because tertiary are more reactive
• the CH3 groups push e- towards the central carbon and there fore weaken the C-O bond
• so the O will fall off more easily

Question 10

What happens in bromination of alcohols?
This is a TWO STEP reaction.

Answer 10

• add a mixture of KBr and concentrated H2SO4 to the alcohol
  1. KBr + H2SO4 -> KHSO4 + HBr
  2. HBr + C2H5OH -> C2H5Br + H2O

This is a nucleophilic substitution reaction.

Question 11

What happens in iodination? This is a TWO STEP reaction.

Answer 11

• add a mixture of red phosphorus and iodine
• then heat under reflux
  1. 2P + 3I2 -> 2PI3
  2. 3C2H5OH + PI3 -> 3C2H5I + H3PO3

Question 12

What conditions are needed for the elimination of alcohol? (aka dehydration)

Answer 12

• heat with concentrated phosphoric (V) acid
• OR heat with NaOH/KOH in ethanolic solution
• this makes alkenes

Question 13

What is a Z isomer

Answer 13

when both groups with the higher priority lie on the same side (top or bottom) of the C=C double bond

Question 14

What is an E isomer

Answer 14

When both groups with the higher priority lie on opposite sides (top and bottom) of the C=C double bond

Question 15

Whats a hydrocarbon

Answer 15

a compound made of hydrogen and carbon only

Question 16

What is a skeletal formula

Answer 16

shows how the atoms are arranged, but without showing carbons

Question 17

whats a homologous series

Answer 17

compounds with the same functional group that differ in formula only

Question 17

what is a functional group

Answer 17

a group of atoms within a molecule that has specific chemical properties

Question 18

whats an isomer

Answer 18

molecules with the same molecular formula but whose atoms are arranged differently

Question 19

whats a structural isomer

Answer 19

molecules with the same molecular formulae but different structural formula

Question 20

what are the three kinds of structural isomerism

Answer 20

positional
functional
chain

Question 21

what is stereoisomerism

Answer 21

molecules with the same structural formula but with different arrangements in space

Question 22

What kinds of stereoisomerism are there

Answer 22

E-Z
Optical

Question 23

whats catalytic cracking

Answer 23

using a zeolite catalyst and heat to break long hydrocarbons into shorter hydrocarbon chains and small alkenes such as ethene

Question 24

whats a biofuel

Answer 24

fuels made form plant components

Question 25

what is a free radical

Answer 25

a species with an unpaired electron

Question 26

whats homolytic fission

Answer 26

where a bond breaks and one electron goes to each atom that was participating in the bond, forming free radicals

Question 27

whats heterolytic fission

Answer 27

where a bond breaks and both electrons in the bond go to one atom that was participating in the bond, forming ions

Question 28

free radical substitution steps

Answer 28

initiation - formation of free radicals using UV light propagation - free radical reacts a non-free-radical species, forming more free radicals as well as new molecules termination - two free radicals meeting and forming a bond

Question 29

whats a carbocation

Answer 29

species with positively charged carbon

Question 30

whats a primary, secondary and tertiary carbocation

Answer 30

one,two and three alkyl group/s directly bonded to positively charged carbon

Question 31

what is the trend in carbocation stability and explain jjt

Answer 31

it increases as the alkyl group number increases because of the positive inductive effect from the alkyl groups, as they push their electrons towards other things, in this case the positive carbocation therefore, the positive charge is reduced and the carbocation becomes more neutral, more stable

Question 32

alkene to alkane mech

Answer 32

H2, Ni catalyst

Question 33

alkane to alkene mech

Answer 33

zeolite catalyst

Question 34

alkane to haloalkane mech

Answer 34

gaseous X2 and UV light

Question 35

alkene to haloalkane mech

Answer 35

gaseous HX

Question 36

haloalkane to alcohol mech

Answer 36

NaOH (aq), reflux

Question 37

haloalkane to nitrile mech

Answer 37

KCN, ethanolic solution, reflux

Question 38

haloalkane to amine mech

Answer 38

conc NH3, heat in a sealed tube

Question 39

alkene to alcohol mech

Answer 39

steam, H3PO4 catalyst