Introduction to Organic Chemistry

Question 1

What is a molecular formula? (1 mark)

Answer 1

⦾ Actual no. of atoms of each element in compound (1)

Question 2

What is a structural formula? (2 marks)

Answer 2

⦾ Arrangment of atoms carbon by carbon (1)
⦾ with attached hydrogens + functional groups (1)
e.g. ⦾ Ethane: CH3CH3
⦾ Pen-1-ene: CH3CH2CH2CHCH2

Question 3

What is a displayed formula? (2 marks)

Answer 3

⦾ All atoms arrangment (1)

⦾ and all bonds between them (1)

Question 4

What is an empirical formula? (1 mark)

Answer 4

⦾ Simplest whole no. ratio of atoms of each element in compound (1)

Question 5

What is a general formula? (1 mark)

Answer 5

⦾ Algebraic formula that can describe any member of a family of compounds.

Question 6

What is a skeletal formula? (3 marks)

Answer 6

⦾ Shows bonds of carbon skeleton (1)
⦾ (and) non-carbon atoms (1)
⦾ H + C atoms that are part of main C chain not shown (1)
⦾ Vertices are Cs

Question 7

What is a homologous series? (4 marks)

Answer 7

Series of molecules with: 
⦾ Same functional group (1)
⦾ Same general formula (1)
⦾ React similarly (1)
⦾ Increase in bp.s as chain length increases (1)

Question 8

Explain alkanes fully? (5 marks)

Answer 8

⦾ CnH2n+2 (1)
⦾ End in: -ane (1)
⦾ Only H + C (1)
⦾ Each C atom has 4 SINGLE BONDS (1)
⦾ SATURATED (1)

Question 9

Explain halogenoalkanes fully? (3 marks)

Answer 9

⦾ Similar to Alkanes EXCEPT (+) 1 H atoms replaced with HALOGEN atom (1)
⦾ Prefix: fluoro-, chloro-, bromo- or iodo- (1)
⦾ Even replace all Hs with halogen atom (1)

Question 10

Explain cycloalkanes fully? (5 marks)

Answer 10

⦾ Ring of C atoms with 2 Hs attached to each C (1)
⦾ CnH2n (1)
⦾ Still saturated (1)
⦾ cyclo- (1)
⦾ -ane (1)
⦾ e.g. 3 Cs needed to make ring so CYCLOPROPANE is smallest cycloalkane - C3H6

Question 11

Explain branched alkanes fully? (4 marks)

Answer 11

⦾ Alkane that doesn’t have all C atoms in 1 straight chain (1)
⦾ Main (longest) C chain + (+) 1 Cs coming off main chain (1)
⦾ Branches - ALKYL groups (1)
⦾ CnH2n+2 (1)

Question 12

What does the ‘3’ in 3-ethylpentane mean? (1 mark)

Answer 12

⦾ branch is on the 3rd C along main chain (1)

Question 13

Explain alkenes fully? (5 marks)

Answer 13

⦾ HC with (+)1 C=C (1)
⦾ CnH2n (1)
⦾ Cs of C=C only bonded to 3 atoms each rather than max of 4 (1)
⦾ So they can form another bond so they’re UNSATURATED (1)
⦾ (makes them) reactive (1)

Question 14

1. The general formula CnH2n only applies to alkenes with… (1 mark)

Answer 14

⦾ …exactly 1 C=C bond (1)

Question 15

Explain alcohols fully? (4 marks)

Answer 15

⦾ -OH group (1)
⦾ CnH2n+1OH (1)
⦾ -ol (1)
⦾ React to give alkenes (1)

Question 16

Explain aldehydes fully? (3 marks)

Answer 16

⦾ End of C chain has:   
  O
   ll
- C - H                          (1)
⦾ R-CHO (R is alkyl group) or an H atom (1)
⦾ -al (1)

Question 17

Explain ketones fully? (3 marks)

Answer 17

⦾ C=O bond except its in middle
      O
       ll
R' - C - R' (1)
⦾ R + R' are alkyl groups which may/may not be the same (1)
⦾ R - CO - R' (1)

Question 18

Explain carboxylic acids fully? (3 marks)

Answer 18

⦾ Contain functional group: 
   O
    ll
 - C - OH  (1)
⦾ -oic acid (1)
⦾ R-COOH (1)

Question 19

What does Nomenclature mean? (1 mark)

Answer 19

⦾ Naming organic compounds (1)

Question 20

Why is the IUPAC system more benficial? (2 marks)

Answer 20

⦾ Scientific ideas communicated across the globe more effectively (1)
⦾ Easier for scientists to get on with testing each other’s work + either support or dispute new theories (1)

Question 21

How do you name straight-chain alkanes? (3 marks)

Answer 21

1. 1st: no. of C atoms in molecule (1)
2. 2nd: “-ane” (1)
3. e.g pentane (5 C atoms) (1)

Question 22

How do you name branched alkanes? (3 marks)

Answer 22

1. no. of C atoms in longest chain + work out stem (meth-, eth-, prop-, but-) (1)
2. Name side chains - according to no. of C atoms they have + which C atom they’re attached to (1)
3. If there’s (+) 1 side chain in molecule, place them in alphabetical order. i.e. but- before eth- groups (1)
   ⦾ e.g. 2-methylbutane. 3-ethyl-2-methylpentane

Question 23

How do you name cycloalkanes? (4 marks)

Answer 23

1. Same name as straight chain alkane but with cyclo- (1)
2. If alkyl group attached, add alkyl prefix (1)
3. If there’s (+) 1 alkyl group, make the numbers as low as possible (1)
4. Alkyl that alphabetically 1st goes on the C (1)
   ⦾ e.g. 1-ethyl-3-methyl-cyclopentane

Question 24

How would you name other functional groups? (3 marks)

Answer 24

1. Stem is longest C chain containing functional group (1)
2. Prefixes + suffixes come from functional groups as well as any alkyl side chains (1)
3. If you need to use no. to show the position of the functional group, give the C which the functional group attached lowest no. possible (1)

Question 25

How do you name alkenes? (2 marks)

Answer 25

⦾ Find stem no. (1)

⦾ -ene (1)

Question 26

If there’s more than 1 functional group, you have to work out which one has the highest priority.
What is the priority list? (1 mark)

Answer 26

Highest priority:
1. Other functional groups
2. Alkenes
3. Alkyl groups
4. Halogens
Lowest priority: (1)
Stem of name comes from longest C chain containing the main functional group.
Number Cs so main functional group has the lowest number possible.
e.g. 3-chloropropan-1-ol 
e.g. 4-chloro-2,2-dimethybutanal
e.g. pent-4-e-2-one

Question 27

1. What are structural isomers? (2 marks)

2. What are the 3 types?

Answer 27

1. ⦾ (Compounds with the) same molecular formula but (1)
   ⦾ different structural / displayed / skeletal formula (1)
2. ⦾ Chain isomers (1)
   ⦾ Position isomers (1)
   ⦾ Functional group isomers (1)

Question 28

Explain what chain isomers are? (2 marks)

Answer 28

⦾ Same functional groups (1)
⦾ but different arrangement of C skeleton (1)

⦾ Some straight chains + others are branched in different ways.

Question 29

Explain what position isomers are? (1 mark)

Answer 29

⦾ Functional group of molecule in different position of C chain (1)

Question 30

Explain what functional group isomers are? (1 mark)

Answer 30

⦾ Different arrangment of same molecular formula (1)

⦾ so molecule has different functional group

Question 31

Explain what stereoisomers are? (2 marks)

Answer 31

⦾ (Compounds / molecules with) the same structural formula (1)
⦾ with atoms / bonds / groups arranged differently in space (1)
OR atoms / bonds / groups with different spatial arrangements

Question 32

Give a type of stereoisomerism? (1 mark)

Answer 32

⦾ E-Z isomerism (1)

Question 33

Explain E-Z isomerism? (3 marks)

Answer 33

⦾ Limited rotation around C=C (1)
⦾ E - (German for apart) opposite + apart (diagonal) (1)
⦾ Z - (German for together) together + same side (horizontal) (1)

Question 34

Explain Cahn-Ingold-Prelog (CIP) Priority Rules?

2 marks

Answer 34

⦾ Atom/group on each side of C=C with higher Ar/Mr given higher priority (1)
⦾ Determine E or Z isomerism (1)

Question 35

Br Cl What is the type of isomerism shown in this
l l molecule? (3 marks)
C = C
l l
F H

Answer 35

⦾ Br has higher Ar than F - Br is higher priority (1)
⦾ Cl has higher Ar than H - Cl is higher priority (1)
⦾ Therefore Z isomer (1)

Question 36

What do curly arrows show? (1 marks)

Answer 36

⦾ movement of e- (1)