Introduction to Organic Chemistry

Question 1

Define molecular formula

Answer 1

the actual number of atoms of each element in a molecule

Question 2

Define empirical formula

Answer 2

simplest ratio of atoms of each element in a compound

Question 3

Define general formula

Answer 3

number of atoms of each element in a substance which has n carbon atoms

Question 4

Define structural formula

Answer 4

this shows the arrangement of atoms in a molecule without showing every bond

Question 5

Define displayed formula

Answer 5

this shows all the bonds and atoms in a molecule

Question 6

Define skeletal formula

Answer 6

this uses lines to represent bonds, each point represents a carbon and hydrogen atoms aren’t shown

Question 7

What is a hydrocarbon

Answer 7

a compound that contains only carbon and hydrogen

Question 8

What are saturated hydrocarbons

Answer 8

• contain single carbon-carbon bonds
• alkanes
• general formula CnH2n+2

Question 9

What are unsaturated hydrocarbons

Answer 9

• at least one multiple bond between carbon atoms
• alkenes (double bond)
• alkynes (triple bond)
• general formula CnH2n

Question 10

What is a homologous series

Answer 10

a family of compounds containing the same functional group but with each successive member of the series differing by a CH2 group

Question 11

What are the trends in homologous series

Answer 11

• trends in physical properties
• an increase in CH2 group is an increase of Mr by 14
• melting and boiling points increase as the chain length increases

Question 12

What is a functional group

Answer 12

an atom/group responsible for the characteristic reactions of the compound

Question 13

What is an aromatic compound

Answer 13

compounds containing a benzene ring, they are unsaturated hydrocarbons and have the formula C6H6

Question 14

What are the IUPAC rules for nomenclature

Answer 14

• find the longest C chain
• give the alkyl group the lowest number
• list alkyl groups alphabetically
• double bond/halogens have priority over alkyl groups
• constants cant be next to constant so add ‘a’

Question 15

What homologous series have their functional group always at the end

Answer 15

1. carboxylic acids (-oic)
2. aldehydes (-al)
3. nitriles (-nitrile)

Question 16

Define structural isomerism

Answer 16

molecules with the same molecular formula but a different structural formula

Question 17

What is chain isomerism

Answer 17

carbon chain is arranged differently

Question 18

What is positional isomerism

Answer 18

position of functional group changes

Question 19

What is functional group isomerism

Answer 19

same atoms but a different functional group

Question 20

What is stereoisomerism

Answer 20

when molecules have the same structural formula but have a different arrangement of atoms in space

Question 21

When does E/Z stereoisomerism occur

Answer 21

it is caused by the limited rotation about the C=C double bonds

criteria for a compound:
- must have a C=C double bond
- each carbon of the C=C must have 2 different groups attached to it

Question 22

How are E and Z isomers decided

Answer 22

• if the groups of higher priority are on the same side of the double bond it is Z ISOMERISM
• if the groups of higher priority are on diagonally opposite sides of the double bond it is E ISOMERISM

Question 23

Explain how the Cahn-Ingold-Prelog (CIP) priority rules can be used to deduce which isomer it is

Answer 23

1. look at the atoms attached directly to the carbon atoms and decide which of the 2 atoms has the highest priority
2. if the 2 atoms attached to a carbon atom are the SAME, then you will need to find the first point of difference - the group with the higher atomic number at the first difference is given higher priority