4.1 - basic concepts and hydrocarbons

Question 1

What is nomenclature?

Answer 1

The system of naming compounds

Question 2

Hydrocarbons are made up of molecules that contain only hydrogen and carbon atoms. When you look at their structures, you can classify them as: (give 3 classifications and their definitions)

Answer 2

• aliphatic hydrocarbons: in which the carbon atoms are joined together in either straight (unbranched) chains or branched chains
• alicyclic hydrocarbons: in which the carbon atoms are joined together in a ring structure but are not aromatic
• aromatic hydrocarbons: in which there is at least one benzene ring in the structure

Question 3

Define homologous series

Answer 3

A homologous series is a series of organic compounds that have the same functional group with successive members differing by CH2

Question 4

Give the first ten prefixes of alkanes and alkenes

Answer 4

1) meth
2) eth
3) prop
4) but
5) pent
6) hex
7) hept
8) oct
9) non
10) dec

Question 5

What are alkanes?

Answer 5

The simplest homologous series is the alkanes. They are aliphatic saturated hydrocarbons, so they contain only carbon and hydrogen joined by single covalent bonds.

Question 6

What three rules do you need to consider when naming an organic compound?

Answer 6

stem - the main part of the name; generated by identifying the longest carbon chain or parent chain

suffix - the end of the name; identifies the most important functional group

prefix - the front part of the name; identifies the other functional groups and the carbon atoms they are attached to

Question 7

Name the first ten alkyl groups (these are known as the stem)

Answer 7

1) methyl
2) ethyl
3) propyl
4) butyl
5) pentyl
6) hexyl
7) heptyl
8) octyl
9) nonyl
10) decyl

Question 8

Define a saturated compound

Answer 8

Saturated compounds have only single bonds

Question 9

Define functional group

Answer 9

A functional group is a group of atoms that is responsible for the characteristic chemical reactions of a compound

Question 10

What four things should you remember when naming compounds?

Answer 10

1) numbers are used to indicate which carbon atom an alkyl group is joined to
2) dashes are used to separate numbers from words
3) commas are used to separate numbers
4) prefixes are written in alphabetical order using the smallest numbers possible to indicate which carbon atoms they are joined to

Question 11

No number is needed when naming aldehydes because this functional group is always on a terminal (end) carbon atom. For organic compounds with more than one identical group, add…

Answer 11

• ‘di-‘ to show two of the same group
• ‘tri-‘ to indicate three of the same group
• ‘tetra-‘ to describe four identical groups

Question 12

What is the general formula of alkanes?

Answer 12

CnH2n+2

Question 13

Define general formula

Answer 13

A general formula is the simplest algebraic formula for a homologous series

Question 14

Define display formula

Answer 14

A displayed formula shows the relative positions of atoms and the bonds between them

Question 15

Define structural formula

Answer 15

A structural formula provides the minimum detail for the arrangement of atoms in a molecule

Question 16

What five steps can you use to work out the empirical formula?

Answer 16

1) change the percentages to masses
2) calculate the number of moles in each element using: amount in moles = mass/RFM
3) divide by the smallest value
4) change the ratio to whole numbers
5) write the formula

Question 17

You can use a three-step method to generate the molecular formula from the empirical formula and molecular mass. What are these three steps?

Answer 17

1) calculate the relative empirical mass using the empirical formula
2) divide the relative molecular mass by the empirical formula mass
3) multiply each atom in the empirical formula by the number calculated in step 2 and write the molecular formula

Question 18

Define skeletal formula

Answer 18

a skeletal formula is a simplified structural formula drawn by removing hydrogen atoms from alkyl chains

Question 19

Define unsaturated

Answer 19

Unsaturated organic chemicals contain at least one carbon-carbon double covalent bond

Question 20

Define structural isomer

Answer 20

Structural isomers are compounds with the same molecular formula but different structural formulae

Question 21

Define stereoisomers

Answer 21

Stereoisomers are organic compounds with the same molecular formula and structural formula but having a different arrangement of atoms in space

Question 22

Define Cis-trans isomerism

Answer 22

Cis-trans isomerism is a type of E/Z isomerism in which the two substituent groups attached to both carbon atoms of the C=C bond are the same

Question 23

Define E/Z isomerism

Answer 23

E/Z isomerism is a type of steeoisomerism caused by the restricted rotation around the double bond -two different groups are attached to both carbon atoms of the C=C double bond

Question 24

Structural isomers are compounds with the same molecular formula but different structural formula. In what three ways can this happen?

Answer 24

• the alkyl groups are in different places
• the functional group can be bonded to different parts of the parent chain
• the functional group could be different

Question 25

Define reaction mechanisms

Answer 25

Reaction mechanisms are the models that show the movement of electron pairs during a reaction

Question 26

Define curly arrows

Answer 26

Curly arrows model the flow of electron pairs during reaction mechanisms

Question 27

Define homolytic fission

Answer 27

Homolytic fission happens when each bonding atom receives one electron from the bonded pair, forming two radicals

Question 28

Define radicals

Answer 28

Radicals are species with one or more unpaired electrons

Question 29

Define heterolytic fission

Answer 29

Heterolytic fission happens when one bonding atom receives both electrons from the bonding pair

Question 30

What happens in the initiation step and what conditions are required?

Answer 30

A free radical is created.

UV light or temperatures of about 300 degrees C are needed