Organic III

Question 1

what is the group for amines

Answer 1

R-NH2

Question 2

what is the group for amides

Answer 2

R-C=O-NH2

Question 3

What is the trend for boiling points of amines compared to alkanes and alcohols

Answer 3

highest bp = alcohol
amines
lowest = alkanes

alcohols have the oxygen with two lone pairs so has all three IMF
amines have the nitrogen with one lone pair so has all three IMF
alkanes only have london forces
HOWEVER
Oxygen is more electronegative than nitrogen and so will form stronger hydrogen bonds, therefore having a higher boiling point

Question 4

What makes amines basic

Answer 4

The lone pair of nitrogen will accept protons
The alkyl groups will push electrons towards the N
this will stablise the positive charge that forms when R- NH3+

Question 5

Preparation of amines from haloalkanes looks like what

Answer 5

haloalkane + ammonia -> primary amine + ammonium halide

Question 6

Preparation of amines from nitriles by reduction looks like what (theres two options)

Answer 6

nitrile + H2 gas -> (Ni catalyst) amine

Use LiAlH4 in dry ether

Question 7

what are some important properties to know about benzene

Answer 7

its an arene
its aromatic
its carcinogenic
colourless liquid

Question 8

what are the issues with the kekule structure

Answer 8

all the bond lengths are the same
all the carbons seem equivalent
the enthalpy of hydrogenation is too small
despite seeming unsaturated, benzene doesnt readily undergo addition reactions

Question 9

why are the bonds in benzene not all the same length

Answer 9

C=C bonds are shorter than C-C bonds
theres stronger electrostatic attractions between the two nuclei and two bonding electron pairs in a C=C bond than in a C-C bond

Question 10

describe the structure of benzene

Answer 10

6 carbons, 6 hydrogens
cyclo structure
pi system created by the ‘resonance’ of the pi bonds around the structure

Question 11

how does the new structure of benzene explain that benzene doesn’t readily undergo addition reactions

Answer 11

the ‘double bond’ is more than 1.5 bonds
so its less electron dense
so less attractive to electrophiles
less susceptible to be attacked by electrophiles

Question 12

draw 1,2 dichlorobenzene

Answer 12

match to notes

Question 13

draw benzenoic acid

Answer 13

match to notes

Question 14

draw 1,4 dichlorobenzenoic acid

Answer 14

match to notes

Question 15

draw phenol

Answer 15

match to notes

Question 16

draw 2 phenyl butane

Answer 16

match to notes

Question 17

what are the reactions of benzene

Answer 17

combustion
hydrogenation
electrophilic substitution
nitration
friedel-crafts alkylation and acylation

Question 18

what happens when benzene is combusted

Answer 18

usually incomplete combustion
burns with a smoky, sooty flame

Question 19

how does benzene hydrogenate

Answer 19

same as alkenes
mix with H2, under pressure with a Ni catalyst

Question 20

how does benzene do electrophilic sub

Answer 20

swaps a H for something else
Heat under reflux with a halogen and a catalyst
Catalyst can include AlX3, FeX3

Question 21

how does benzene do nitration

Answer 21

this is a specific electrophilic sub
heat (50-55 degrees), under reflux, with conc. HNO3 + conc H2SO4

Question 22

how does benzene do friedel crafts reactions for alkylation

Answer 22

use a haloalkane
with AlCl3 catalyst

Question 23

how does benzene do friedel-crafts reactions for acylation

Answer 23

used an acid chloride
with AlCl3 catalyst

Question 24

What are some properties of phenol

Answer 24

low solubility in water
weakly acidic
more reactive than benzene

Question 25

why is phenol weakly acidic

Answer 25

the lone pair on the O of -OH delocalises into the pi system on the ring. So electron density increases around the benzene ring SO the O-H bond weakens So sometimes the H will fall off as H+, making it in solution slightly acidic

Question 26

why is phenol more reactive than benzene

Answer 26

the lone pair of electrons on the O of OH delocalises into the pi system so the electron density in the pi ring of the benzene ring increases phenol becomes more electron dense, so it is more susceptible to be attacked by electrophiles and thus is more reactive

Question 27

why will phenol only undergo electrophilic SUB

Answer 27

to maintain the pi system, which keeps the molecule stable

Question 28

why do we keep nitration of benzene at a temperature of 50-55, but not higher

Answer 28

multiple substitutions will occur, forming explosive materials such as trinitrotoluene

Question 29

explain why phenol reacts with nitric acid more readily than benzene

Answer 29

the lone pair of the O in the -OH delocalises into the pi system on the benzene ring of phenol so phenol becomes more electron dense in its pi system than benzene is this makes phenol more susceptible to be attacked by electrophiles

Question 30

what is the formula of a Grignard reagent

Answer 30

RMgX X = halogen R = alkyl or aryl group

Question 31

what are some drying agents

Answer 31

CaSO4, CaCl2, Na2SO4, MgSO4

Question 32

why is the C in CO2 delta positive

Answer 32

O is more eletronegative than C, so pulls electrons closer to themselves away from the O so O is less negative

Question 33

why is esterification via acyl chlorides better than via carboxylic acids

Answer 33

it is irreversible

Question 34

draw out steps needed to convert chloroethane to ethanoic acid, with conditions and reagents

Answer 34

NaOH (aq) to form ethanol H+/Cr2O72- with reflux to form COOH

Question 35

chloroethane to aminoethane

Answer 35

conc NH3, in a sealed container and heated, ethanolic

Question 36

draw out the steps needed to convert chloroethane to ethyl ethanoate

Answer 36

NaOH (aq) to ethanol, H+/Cr2O7 2- to COOH, + ethanol + H2SO4 catalyst to ester