1. Introduction To Organic Chemistry

Question 1

Define empirical formula

Answer 1

Simplest formula that shows the ratio of number of each kind of atoms of elements present in one molecule

Question 2

Define nucleophile (Lewis base)

Answer 2

Electron pair donor and has a lone pair of electrons to be donated

Question 3

Define electrophile (Lewis acid)

Answer 3

Electron pair acceptor and is electron deficient

Question 4

Define homolytic fission

Answer 4

Covalent bond is broken such that each of the bonding atoms takes one of the bonding electrons, giving rise to free radicals (species with unpaired electrons)
Energy must be supplied (light) to break the strong covalent bond –> free radicals formed possess this energy and are thus very reactive

Question 5

Define heterolytic fission

Answer 5

Covalent bond is broken such that one of the bonding atoms takes both bonding electrons (and becomes an anion) while the rest of the molecules become a cation

Question 6

Define addition reaction

Answer 6

Reaction where two or more molecules combine to form a single product
The attacking reagent adds across an unsaturated bond on the reactant

Question 7

Define substitution reaction

Answer 7

Reaction which involved the replacement of an atom or group of atoms (leaving group) by another atom or group of atoms

Question 8

Define elimination reaction

Answer 8

Reaction which involves the loss of a small molecule from one larger molecule, giving rise to an unsaturated product

Question 9

Define condensation (addition-elimination) reaction

Answer 9

Reaction which involves the joining of two molecules, with the loss of a small molecule in the process

Question 10

Define hydrolysis reaction

Answer 10

Reactions involving water

Question 11

Define oxidation reaction

Answer 11

Reactions which involve the removal of H and / or addition of O

Question 12

Define reduction reaction

Answer 12

Reactions which involve removal of O and / or addition of H

Question 13

Define constitutional/structural isomerism

Answer 13

Compounds with the same molecular formula but different structural formula

E.g. Chain isomers, positional isomers, functional group isomers

Question 14

Define stereoisomerism and state the two types of stereoisomerism

Answer 14

Same molecular and structural formula but differ in the spatial arrangement of their atoms

Geometrical/cis-trans isomers and enantiomers/optical isomers

Question 15

State the conditions for cis-trans isomerism and the properties of geometrical isomers

Answer 15

Conditions:

• restricted rotation about a C=C bond i.e. in alkenes
• two different groups/atoms attached to each carbon atom of the C=C bond

Properties:
-Generally have different physical properties and in some cases, different chemical properties too

Question 16

Define enantiomers

Answer 16

Stereoisomers which are non-superimposable mirror images, arising due to the presence of a chiral carbon centre

Question 17

State the properties of enantiomers

Answer 17

• Identical physical properties except their effect on plane polarized light –> A pair of enantiomers rotate plane-polarized light by equal but opposite angles
• Identical chemical properties except when interacting with other chiral molecules e.g. chiral drugs with chiral enzyme active sites

Question 18

Define molecular formula.

Answer 18

Actual number of each kind of atoms present in one molecule