Unit 4, Topic 1: Introduction to organic materials

Question 1

Organic chemistry

Answer 1

study of carbon-based compounds

Question 2

Hydrocarbon

Answer 2

organic compound continuing only hydrogen and oxygen

Question 3

Functional group

Answer 3

atom or group of atoms which gives a set of characteristics to a molecule containing those atoms

Question 4

Empirical formula

Answer 4

simplest whole number ratio of atoms in a compound

Question 5

Molecular formula

Answer 5

actual number of atoms of each type

Question 6

Structure formula

Answer 6

indication of structure but also number of atoms of each type o Extended or condensed

Question 7

Alkane

Answer 7

General formula – CnH2n+2
* Saturated – only contains single C-C bonds
* Each member of the homologous series is separated by -
CH2-
* Homologous series – sequence of compounds sharing
similar properties and functional groups

Question 8

Alkanes - naming

Answer 8

• Straight chain – all carbon atoms in one chain
• Branched chain – at least one group attached to main
  chain
  1. Look for longest continuous carbon chain
  2. Check for alkyl side groups
  3. If alkyl groups are present, number parent chain so the branch is the smallest
  4. If the alkyl group can only be in that one space – no need to number
  5. Place the number and position of each group before parent name
  6. Use ‘di’ for two identical branches, ‘tri’ for three
  7. Arrange alkyl groups in alphabetical order
  8. Name is one continuous name

Question 9

Alkanes - properties

Answer 9

Non-polar – only dispersion forces
* Higher molecular mass = more electrons = greater dispersion forces
* Up the homologous series – boiling point increases
o Increase in IMFs – more energy (heat) needed to break them
o Boiling point also is known as volatility – more volatility = lower boiling point

• Melting point is similar trend but not linear
  o Even numbered chains pack together more tightly as a solid and have stronger attractive
  forces – higher melting point

Question 10

Alkane - solubility

Answer 10

Alkanes non-polar – doesn’t dissolve in polar
substances like water
* Alkanes will dissolve in polar substances – e.g.
tetrachloromethane
* Energy to break existing dispersion forces is low –
new dispersion forces form between molecules
which are releasing energy – compensates for energy
required to break initial dispersion forces
* Miscible – able to form homogenous mixtures

Question 11

Alkane branching

Answer 11

Decreases surface area as more compact
* Molecular shape influences IMF strength
* Straight chain hydrocarbons have higher boiling
points vs branched ones
o Straight chain molecules fit together more
compactly – closer = stronger IMFs
* Melting point is more complicated
o Branching decreases boiling point – more
compact and less SA
o But can also increase boiling point due to
symmetry etc. – due to more branched
molecules being more spherical and thus more packable into a crystal lattice

Question 12

Alkane - reactions of alkanes

Answer 12

Tend to be unreactive – saturated with only single
bonds
* Undergo substitution reactions
* Halogen substitution occurs
o UV light is needed to break the bond
between halogen atoms
o UV light acts as catalyst
o Further substitution can occur if halogen is in excess
* Combustion
o Reacts with oxygen in an exothermic reaction creating CO2, H2O and energy

Question 13

Cycle alkanes

Answer 13

• Alkanes arranged in a circular/ring
  shape
• Saturated hydrocarbon
• General equation – CnHn

Question 14

Alkenes

Answer 14

• Alkenes are unsaturated (at least one C=C, C≡C bond)
• C=C bond give them their properties – occurs when 2 pairs of electrons are shared
• General formula – CnH2n
• Shape is trigonal planar – due to VSEPR theory

Question 15

Alkenes - naming

Answer 15

1. Use -ene as suffix
2. Number the double bond on the lowest number
3. Number side group based on lowest C=C number
4. If more then 1 side group – identify by name and number
5. If side groups are the same – use di-/tri- etc
6. Insert number after stem e.g. but-1-ene

Question 16

Alkenes - structural isomerism

Answer 16

Refers to same molecule but different order of atom
attachment
* Stereoisomerism is when atom arrangement has same
structure but different arrangements in space
* Key type is Cis/Trans – geometric isomerism
* Due to C=C bond – hinders rotation and locks atoms onto
one side
o C-C has free rotation – no cis/trans isomerism
* For cis/trans isomerism to occur, each carbon atom needs to be attached to two different groups
o Groups can be H atoms, alkyl or functional groups
o If on same side – cis, if on opposite – trans