Organic Chemistry

Question 1

no. of molecular orbitals

Answer 1

equal to the number of atomic orbitals that combine

Question 2

end-on overlap of orbitals

Answer 2

form sigma bonds

Question 3

side-on overlap of orbitals

Answer 3

form pi bonds

Question 4

hybridisation

Answer 4

the process of mixing orbitals within an atom to create a set of (degenerate) hybrid orbitals

Question 5

hybridisation of alkanes

Answer 5

the 2s orbital and the three 2p orbitals form four degenerate sp3 hybrid orbitals, forming sigma bonds

Question 6

hybridisation of alkenes

Answer 6

the 2s orbital and two of the 2p orbitals hybridise to form three degenerate sp2 hybrid orbitals, forming both sigma and pi bonds

Question 7

benzene electrons

Answer 7

are delocalised, and have both sigma and pi bonds, with the pi system extending across all six carbons

Question 8

hybridisation of alkynes

Answer 8

a 2s orbital and a 2p orbital hybridise to form a sigma and two pi bonds with 2 degenerate hybrid orbitals.

Question 9

HOMO

Answer 9

highest occupied molecular orbital. electrons fill orbitals, leaving higher orbitals unfilled

Question 10

LUMO

Answer 10

lowest unoccupied molecular orbitals

Question 11

movement of electrons from HOMO to LUMO

Answer 11

absorption of electromagnetic energy can cause electrons to be promoted from HOMO to LUMO

Question 12

colour of organic molecules

Answer 12

large energy difference between HOMO and LUMO leads to the molecule absorbing ultraviolet light

Question 13

chromophore

Answer 13

a group of atoms within a molecule that is responsible for absorption of light in the visible region of the spectrum

Question 14

chromophore and colour in molecules

Answer 14

light can be absorbed when electrons in a chromophore are promoted from the HOMO to the LUMO

Question 15

conjugated system

Answer 15

a system of adjacent unhybridised p orbitals that overlap side-on to form a molecular orbital across a number of carbon atoms. electrons in these systems are delocalised. molecules with alternating single/double bonds have conjugated systems. chromophores also exist in molecules with a conjugated systems

Question 16

conjugated system and HOMO/LUMO

Answer 16

the more atoms in the conjugated system the smaller the gap between HOMO and LUMO, so a lower frequency of light is absorbed by the compound. complementary colour produced

Question 17

homolytic fission

Answer 17

when a bond splits evenly. usually occurs when non-polar covalent bonds are broken

Question 18

heterolytic fission

Answer 18

occurs when a bond splits unevenly. normally occurs when polar covalent bonds are broken

Question 19

nucleophiles

Answer 19

anions or neutral molecules that are electron rich. attracted to molecules with a positive charge. will donate electrons

Question 20

electrophiles

Answer 20

cations or neutral molecules that are electron deficient. attracted to molecules with a negative charge. will accept electrons

Question 21

monohaloalkanes and potassium/sodium hydroxide in ethanol

Answer 21

elimination reaction to form alkenes

Question 22

monohaloalkanes and aqueous alkalis

Answer 22

nucleophilic substitution to form alcohols

Question 23

monohaloalkanes and alcoholic alkoxides

Answer 23

nucleophilic substitution to form ethers

Question 24

monohaloalkanes and ethanolic cyanide

Answer 24

nucleophilic substitution to form nitriles that can then be hydrolysed to carboxylic acids

Question 25

sN1

Answer 25

nucleophilic substitution reaction with a minimum of two steps with a carbocation intermediate

Question 26

sN2

Answer 26

nucleophilic reaction with a single step and a transition step

Question 27

lithium aluminium hydride

Answer 27

reducing agent

Question 28

ethers

Answer 28

substituted alkanes in which a hydrogen atom is replaced by an alkoxy functional group

Question 29

monohaloalkane and alkoxide

Answer 29

nucleophilic substitution to form an ether

Question 30

markovnikov’s rule

Answer 30

when a hydrogen halide or water is added to an unsymmetrical alkane, the hydrogen atom becomes attached to the carbon with the most hydrogen atoms attached to it already

Question 31

amines + acids

Answer 31

form salts

Question 32

phenyl group

Answer 32

benzene ring in which one hydrogen atom has been substituted by another group. C6H5

Question 33

benzene ring and halogenation

Answer 33

halogen with either aluminium/iron chloride or bromine. (chlorination or bromination)

Question 34

benzene ring and alkylation

Answer 34

using aluminium chloride

Question 35

benzene ring and nitration reactions

Answer 35

using concentrated sulphuric acid and concentrated nitric acid

Question 36

benzene rings and sulfonation

Answer 36

using concentrated sulphuric acid

Question 37

formation of molecular orbitals

Answer 37

two atomic orbitals form a bonding molecular orbital and an antibonding orbital

Question 38

geometric isomerism

Answer 38

can occur when there is restricted rotation, and when each carbon has two different groups attached. labelled cis or trans

Question 39

optical isomers

Answer 39

chiral and are non-superimposable images of each other. also called enantiomers.

Question 40

racemic mixture

Answer 40

a mixture of enantiomers in equal amounts. optically inactive because the rotational effect of the plane-polarised light cancels out

Question 41

a drug

Answer 41

a substance that alters the biochemical processes in the body

Question 42

agonist

Answer 42

mimics the natural compound and binds to the receptor molecules to produce a response similar to the natural active compound

Question 43

anatagonist

Answer 43

prevents the natural compound from binding to the receptor, and so blocks the natural response from occurring

Question 44

enzyme inhibitors

Answer 44

an antagonist that works on an enzyme specifically (binds to the active site)