13: Organic Chemistry Basics ✅

Question 1

electrophilic addition

definition

Answer 1

electron-rich region attacked by electrophile;
followed by addition of small molecule;
forming a single product

Question 2

nucleophilic addition

definition

Answer 2

electron-deficient region attacked by nucleophile;
followed by addition of small molecule;
forming a single product

Question 3

free-radical reaction mechanism

explanation

Answer 3

initiation: breaking covalent bond using energy from natural UV light; forms two free radicals
propagation: free radicals attack reactant molecules, producing more free radicals
termination: two free radicals react with each other to form a product molecule

Question 4

free radical substitution

definition

Answer 4

a substitution reaction involving free radicals as a reactive intermediate using a free radical reaction mechanism

Question 5

nucleophilic substitution

definition

Answer 5

a nucelophile displaces another nucleophile

the displaced nucleophile is the ‘leaving group’

Question 6

homolytic fission

definition

Answer 6

each atom in a molecule takes an electron from their covalent bond to form two free radicals;
the covalent bond is broken

Question 7

heterolytic fission

definition

Answer 7

the more electronegative atom in a molecule takes both electrons from their covalent bond;
positive and negative ions are formed;
the covalent bond is broken

Question 8

initiation

definition

Answer 8

breaking covalent bond in a free-radical reaction mechanism using energy from natural UV light;
forms two free radicals

Question 9

propagation

definition

Answer 9

free radicals attack reactant molecules in a free-radical reaction mechanism, producing more free radicals

Question 10

termination

definition

Answer 10

free radicals react with each other in a free-radical reaction mechanism, to form a product molecule

Question 11

free radical

definition

Answer 11

a species with one or more unpaired electrons

Question 12

hydrocarbon

definition

Answer 12

a compound made up of carbon and hydrogen atoms only

Question 13

sp³ hybridised

Answer 13

refers to carbon atoms that have formed four σ bonds

tetrahedral arrangement with bond angles of 109.5°

Question 14

sp² hybridised

Answer 14

carbon atoms that use only three of their electron pairs to form a σ bond

trigonal planar arrangement; 120°

Question 15

sp hybridised

Answer 15

Carbon atoms that have used only one of their electron pair to form a σ bond

linear arrangement with bond angles 180°

Question 16

arrangement of sp³ hybridised molecule

Answer 16

tetrahedral with 109.5° bond angle

Question 17

arrangement of sp² hybridised molecule

Answer 17

trigonal planar with 120° bond angle

Question 18

arrangement of sp hybridised molecule

Answer 18

linear with 180° bond angle

Question 19

optical isomer / enantiomer

definition

Answer 19

A molecule with a non super-imposable mirror image

Question 20

homologous series

definition

Answer 20

a group of organic compounds that have the same functional group, the same general formula and the same chemical properties

Question 21

unsaturated hydrocarbons

definition

Answer 21

hydrocarbons which contain carbon-carbon double or triple bonds

Question 22

elimination reaction

definition

Answer 22

a reaction in which a small molecule (such as H₂O or HCl) is removed from an organic molecule

Question 23

hydrolysis

definition

Answer 23

a reaction in which a compound is broken down by water, dilute acids or alkalis

Question 24

condensation reaction

definition

Answer 24

a reaction in which two organic molecules join together and in the process eliminate small molecules (such as H₂O or HCl)

Question 25

the two types of hybridised carbons that force the molecule to adopt a planar configuration

Answer 25

sp² hybridised → trigonal planar arrangement
sp hybridised → linear arrangement

Question 26

structural isomerism

definition

Answer 26

when compounds have the same molecular formula but different structural formulae

Question 27

three types of structural isomerism

Answer 27

1. chain isomerism
2. functional group isomerism
3. positional isomerism

Question 28

chain isomerism

Answer 28

when compounds have the same molecular formula, but their longest hydrocarbon chain is not the same

caused by branching

Question 29

positional isomerism

Answer 29

differences in the position of a functional group in each isomer

functional group can be located on different carbons

Question 30

functional group isomerism

Answer 30

When different functional groups result in the same molecular formula, functional group isomers arise

isomers have very different chemical properties because they have different functional groups

Question 31

stereoisomerism

definition

Answer 31

when molecules have the same structural formula but their atoms are arranged differently in space

Question 32

two types of stereoisomerism

Answer 32

1. Geometrical (cis/trans) isomerism
2. Optical isomerism

Question 33

geometrical (cis/trans) isomerism

Answer 33

found in unsaturated/ring compounds
compounds have different physical and chemical properties

Question 34

optical isomerism

Answer 34

when a carbon atom in a molecule is bonded to four different groups of atoms (chiral centre)

Question 35

characteristics of enantiomers

Answer 35

• non super-imposable mirror images of each other
• differ in their ability to rotate the plane of polarised light - one enantiomer will rotate it clockwise and the other anticlockwise
• for every chiral centre, there are 2^n enantiomers in total

Question 36

origin of geometrical (cis/trans) isomerism in unsaturated compounds

Answer 36

groups attached to the C=C carbons remain fixed in their position
* free rotation of the bonds about the C=C bond is not possible due to the presence of a π bond