Pack 2B definitions

Question 1

structural isomers

Answer 1

molecules with the same molecular formula but different structural arrangement of atoms

Question 2

stereoisomers

Answer 2

compounds with the same structural formula but a different arrangement of atoms in space

Question 3

E/Z isomerism

Answer 3

a type of steroisomerism in which different groups attached to each carbon of a c=c double bond may be arranged differently in space due to the restricted rotation of the double bond

Question 4

cis- trans isomerism

Answer 4

is a special type of E/Z isomerism in with there is a non-hydrogen group and a hydrogen on each C of a C=C double bond.
The cis isomer (Z isomer) has has the H atoms on each carbon on the same side .
The trans isomer (E isomer has the H atoms on each carbon on different sides)

Question 5

homolytic fission

Answer 5

the breaking of a covalent bond, with one of the bonded electrons going to each atom forming two radicals.

Question 6

radical

Answer 6

a species with an unpaired electron

Question 7

heterolytic fission

Answer 7

the breaking of a covalent bond where both of the bonded electrons going to one of the atoms forming a cation and a anion.

Question 8

nucleophile

Answer 8

an atom of a group of atoms that is attracted to an electron deficient center or atom where it donates a pair of electrons to form a new covalent bond

Question 9

electrophile

Answer 9

an atom or group of atoms that is attracted to an electron rich atom or center and accepts a pair of electrons to form a new covalent bond

Question 10

addition reaction

Answer 10

a reaction in which a reactant is added to an unsaturated molecule to make a saturated molecule

e.g. ethene + bromine (electrophile) ——> 1,2- dibromoethane

Question 11

substitution reaction

Answer 11

a reaction in which an atom or groups of atoms is replaced with a different atom or group of atoms

e.g. bromoethane + hydroxide ion (nucleophile) —> ethanol + bromide ion

Question 12

elimination reaction

Answer 12

the removal of a molecule from a saturated molecule to make an unsaturated molecule

e.g. ethanol——>ethene + water

Question 13

radical substitution

Answer 13

a type of substitution reaction in which a radical replaces a different atom or group of atoms

Question 14

mechanism

Answer 14

a sequence of steps showing the path taken by electrons in a reaction

Question 15

Initiation

Answer 15

the first step of a radical substitution in which free radicals are generated by ultraviolet radiation

Question 16

Propagation

Answer 16

the two repeated steps in radical substitution that build up the products in a chain reaction

Question 17

Termination

Answer 17

the step at the end of a radical substitution when two radicals combine to form a molecule

Question 18

a Pi bond

Answer 18

the reactive part of a double bond formed above and below the plane of bonded atoms by the sideways overlap of p orbitals.
fixes the carbon atoms in position at either end of the double bond preventing rotation.

Question 19

a sigma bond

Answer 19

bond formed directly between two carbon atoms by the overlap of orbitals

Question 20

polymer

Answer 20

a long molecular chain built up from monomers

Question 21

monomer

Answer 21

small molecule that combines with many other monomers to form a polymer

Question 22

addition polymerisation

Answer 22

the process in which unsaturated alkane molecules (monomers) add on to a growing polymer chain one at a time to form a very long saturated molecular chain.

Question 23

addition polymer

Answer 23

a long molecular chain formed by repeated addition reactions of many unsaturated alkene molecules

Question 24

biodegradable material

Answer 24

material that is broken down naturally in the environment by organisms