Basic concepts of organic chemistry

Question 1

Saturated

Answer 1

Containing single bonds only

Question 2

Unsaturated

Answer 2

Containing a multiple carbon-carbon bond

Question 3

Homologous series

Answer 3

A family of compounds with similar chemical properties, whose successive members differ by the addition of a —CH2— group

Question 4

Functional group

Answer 4

The part of the organic molecule largely responsible for the molecule’s chemical properties

Question 5

Aliphatic

Answer 5

Carbon atoms are joined to each other in unbranched (straight) or branched chains, or non-aromatic rings

Question 6

Alicyclic

Answer 6

Carbon atoms are joined to each other in ring (cyclic) structures, with or without branches

Question 7

Aromatic

Answer 7

Some or all of the carbon atoms are found in a benzene ring

Question 8

Molecular formula

Answer 8

Shows the number and type of atoms of each element present in a molecule

Question 9

Empirical formula

Answer 9

Simplest whole number ratio of the atoms of each element present in a compound

Question 10

General formula

Answer 10

Simplest algebraic formula for any member of a homologous series

Question 11

Displayed formula

Answer 11

Shows the relative positioning of all the atoms in a molecule and the bonds between them

Question 12

Structural formula

Answer 12

Shows clearly which groups are bonded together e.g. CH3(CH2)2CH3

Question 13

Skeletal formula

Answer 13

Simplified organic formula, where all the Cs and Hs are removed and only the bonds between Cs and any functional groups are shown

Question 14

Structural isomerism

Answer 14

Compounds with the same molecular formula but different structural formulae

Question 15

Homolytic fission

Answer 15

Each of the bonded atoms take one of the shared pair of electrons from the bond, forming two radicals with an unpaired electron; represented using fish hook arrows

Question 16

Heterolytic fission

Answer 16

One of the bonded atoms takes both of the electrons from the bond, forming one +ve and one -ve ion; represented using curly arrows

Question 17

Addition reaction

Answer 17

Two reactants join together to form one product

Question 18

Substitution reaction

Answer 18

An atom or group of atoms is replaced by a different atom or group of atoms; 2 reactants –> 2 products

Question 19

Elimination reaction

Answer 19

Involves the removal of a small molecule from a larger one; 1 reactant –> 2 products

Question 20

Stereoisomerism

Answer 20

Have the same structural formula but a different arrangements of atoms in space

Question 21

E/Z isomerism

Answer 21

Arises because rotation about the double bond is restricted and the groups attaches to each carbon atom are therefore fixed relative to each other (caused by pi-bond’s electron density above and below the plane of the sigma-bond)

Requires - a C=C bond and different groups attached to each of these Cs

Question 22

Cis-trans isomerism

Answer 22

Special case of E/Z isomerism, where one of the attached groups on each carbon atom of the double bond must be the same

Question 23

Effect of chain length on boiling points of alkanes

Answer 23

London forces act between molecules in close surface contact, so as chain length increase, surface area increases, allowing more surface contact; London forces will be larger

Question 24

Effect of branching on boiling point

Answer 24

Branched isomers have lower boiling points because branching means there are fewer surface points of contact between molecules (branches get in the way and prevent the molecules getting as close together as possible), resulting in fewer London forces

Question 25

Disposing of waste polymers

Answer 25

Lack of reactivity makes polymers suitable for storing food and chemicals, but also hard to dispose because they are non-biodegradable, causing environmental effects (killing marine life)

Question 26

Recycling

Answer 26

Reduces environmental impact by conserving fossil fuels and decreasing waste going to landfill.
Have to separate polymers, chop into flakes, wash, dry, then melt. Cut into pellets to use.

Question 27

PVC recycling

Answer 27

Hazardous due to high chlorine content (releases toxic gases when burnt). Used to grind before solvents were introduced, so PVC is dissolved, then recovered by precipitation.

Question 28

Using waste polymers as fuel

Answer 28

Polymers that are difficult to recycle can be incinerated to heat homes, etc. (release lots of energy due to their origin from natural gas and crude oil).

Question 29

Feedstock recycling

Answer 29

Chemical and thermal processes that can reclaim monomers, gases or oils from waste polymers. Able to handle unsorted and unwashed polymers.

Question 30

Biodegradable polymers

Answer 30

Polymers made from plant starch, cellulose, plant oils and proteins can be broken down by microorganisms into water, carbon dioxide, etc.

Question 31

Photodegradable polymers

Answer 31

Contain bonds that are weakened by absorbing light to start the degradation.