year 2 organic chem

Question 1

describe benzene

Answer 1

-each C has 3 covalent bonds
-spare electrons overlap
-to form a cloud of delocalised electrons
-planar
-6C compound in a ring structure
-C-C bonds equal in length
-expected enthalpy of hydrogenation is -360
-actual enthalpy is less exothermic by 152
-benzene is more stable

Question 2

conditions for the nitration of benzene

Answer 2

-conc. HNO3
-conc. H2SO4 catalyst

Question 3

equations for the formation of the electrophile for the nitration of benzene

Answer 3

HNO3 + H2SO4 –> H2NO3^+ + HSO4^-

H2NO3^+ –> NO2^+ + H2O

Question 4

reagents, conditions and product for the acylation of benzene

Answer 4

-acyl chloride
-halogen carrier catalyst - AlCl3
-anhydrous
-produces phenylketone

Question 5

2 ways to make aliphatic amines

Answer 5

nucleophilic substitution of a haloalkane with ammonia
reducing a nitrile

Question 6

why is nucleophilic substitution of a haloalkane with ammonia inefficient

Answer 6

-the amine produced is a base so can act as a nucleophile leading to further substitutions with the haloalkane
-until a quaternary ammonium salt is produced which can’t undergo further substitutions
-large XS of ammonia used at start of reaction to give greater yield of primary amine

Question 7

what is the use of quaternary ammonium salts

Answer 7

-cationic surfactant
-used in fabric and hair conditioners

Question 8

reagents and conditions to produce an amine by reducing a nitrile

Answer 8

H2 gas
nickel catalyst

Question 9

compare the base strength of amines

Answer 9

-the more available the lone pair, the stronger the base
-alkyl groups are electron pushing so the electron density on the N atom is increased
-methylamine is a strong base

-benzene is electron withdrawing
-lone pair on N is less available
-phenylamine is weak base

Question 10

how are aromatic amines synthesised

Answer 10

reducing nitrobenzene

Question 11

what are the reagents, conditions and products for reducing nitrobenzene

Answer 11

tin and conc HCl
forms an ionic salt
NaOH is used to neutralise the salt to phenylamine

Question 12

what is phenylamine used for

Answer 12

starting molcule for dyes and pharmaceuticals

Question 13

how are polyesters made

Answer 13

diacyl chloride + dialcohol –> polyester + HCl
-faster but produces hazardous HCl
dicarboxylic acid + dialcohol <–> polyester + water
-slower, reversible

Question 14

example of a polyester

Answer 14

Terylene
benzene-1,4-dioic acid + ethan-1,2-diol

Question 15

how are polyamides made

Answer 15

diacyl chloride + diamine –> polyamide + HCl
-faster but produces hazardous HCl
dicarboxylic acid + diamine <–> polyamide + water
-slower, reversible

Question 16

examples of polyamides

Answer 16

Kevlar
1,4- diaminobenzene + benzene-1,4,-dioic acid
Nylon
1,6-diaminohexane + hexane-1,6-dioic acid

Question 17

compare the the IMF of addition polymers and condensation polymers

Answer 17

-condensation stronger and more rigid
-C-N and C-O bonds in condensation polymers are polar so they have d-p d-p and H bonds between polymers

Question 18

compare the reactivity of addition polymers and condensation polymers

Answer 18

-condensation polymers are more reactive have polar bonds in their chains which can be attacked by nucleophiles
-condensation polymers are therefore biodegradable whereas addition polymers aren’t (strong non-polar covalent bonds)

Question 19

what are optical isomers

Answer 19

-arises when a compound contains a carbon atom with 4 different groups attached to it
-the enantiomers are non-superimposable
-they rotate plane-polarised light in opposite directions

Question 20

what is a racemic mixture

Answer 20

-contains equal quantities of each enantiomer
-has no effect on plane polarised light
-forms due to planar C=O bond so equal chance of nucleophile attacking from above or below bond

Question 21

what are the reactants, conditions and products for the reduction of aldehydes and ketones

Answer 21

-nucleophilic addition
-NaBH4 reducing agent
-produces alcohols

Question 22

what are the reactants, conditions and products for the nucleophilic addition of aldehydes and ketones

Answer 22

-acidified KCN (not HCN as it is a toxic gas)
-produces hydroxynitriles

Question 23

what are the characteristic reactions of carboxylic acids

Answer 23

-same as normal acids
+ metal –> salt + hydrogen
+ carbonate –> salt + water + CO2
+ alkali –> salt + water

Question 24

how are esters formed

Answer 24

carboxylic + alcohol –> ester + water
H2SO4 catalyst

Question 25

uses of esters

Answer 25

-food flavouring/ perfumes -solvent -plasticiser to make plastics more flexible -used to make soap and biodiesel

Question 26

what is the difference between acid and base hydrolysis of esters

Answer 26

acid hydrolysis produces alcohol and carboxylic acid base hydrolysis produces alcohol and carboxylate ion

Question 27

how to make soap

Answer 27

-triester is made from 3 carboxylic acids and glycerol -soap is formed by hydrolysing triesters with conc. NaOH -forms glycerol and sodium salt (soap)

Question 28

how to make biodiesel

Answer 28

-react triester with methanol with KOH catalyst -produces glycerol and a mixture of methyl esters (biodiesel)

Question 29

reactions of acyl chlorides with water, alcohol, conc NH3 and amines

Answer 29

+ water --> carboxylic acid + HCl gas + alcohol --> ester + HCl gas + conc. NH3 --> amide + HCl gas + amine ---> N-substituted amide + HCl gas for acid anhydrides, carboxylic acids replace the HCl gas

Question 30

compare acyl chloride and acid anhydride reactions

Answer 30

-acyl chlorides have more vigorous reactions -acyl chlorides produce HCl gas which is very corrosive. acid anhydrides produce carboxylic acids which are less corrosive -acyl chlorides generally more expensive

Question 31

structure of amino acids at a high and low pH

Answer 31

low pH - NH2 --> NH3^+ high pH - COOH --> COO^- zwitterions have both

Question 32

what is the primary, secondary and tertiary

Answer 32

primary- held by covalent bonds between amino acids via condensation reactions secondary- either a helix or b pleated sheet formed due to H bonds between groups in polypeptide tertiary- held by H bonds, ionic bonds, disulfide bridges and VDW

Question 33

which C of the 2-deoxyribose does the base and phosphate attach to

Answer 33

phosphate - carbon 5 base- carbon 1

Question 34

how many H bonds does each base pair form

Answer 34

C and G form 3 A and T form 2

Question 35

how does cisplatin work as an anti cancer drug

Answer 35

N atom on guanine base in DNA forms coordinate bond with Pt, replacing a chloride ligand another N on guanine in opposite strand replaces the 2nd chlorine DNA disrupted- cant unwind and replicate cells stop dividing

Question 36

evaluate cisplatin

Answer 36

also targets healthy cells that divide frequently e.g. hair to combat this, low dosages are given, targeted to tumour benefits outweigh side effects

Question 37

what standard substance is used in NMR spectroscopy and why

Answer 37

tetramethylsilane (TMS) silicon with 4 methyl groups attached chemically unreactive 12 H atoms in identical environments produces a single peak away from other peaks volatile and easily removed from sample after

Question 38

describe the mobile and stationary phase in chromatography

Answer 38

stationary phase- molecules can't move (either solid or liquid on solid support) mobile phase - molecules can move (always liquid or gas) the mobile phase moves over the stationary phase more soluble/attracted to mobile phase - travels further more retention/attracted to stationary phase moves less

Question 39

how is a crystalline solid separated and purified

Answer 39

-filter -dissolve in min amount of hot solvent -cool and filter under reduced pressure -wash with cold water and dry