11.2 Nonenclature of Organic Compounds

Question 1

What groups can hydrocarbons be classified into?

Answer 1

• Aliphatic
• Alicyclic
• Aromatic

Question 2

What is an aliphatic compound?

Answer 2

• A compound containing carbon and hydrogen joined together in straight chains, branched chains or non-aromatic rings

Question 3

What is an alicyclic compound?

Answer 3

• An aliphatic compound arranged in non-aromatic rings with or without side chains

Question 4

What is an aromatic compound?

Answer 4

• A compound containing a benzene ring

Question 5

List 3 homologous series of aliphatic hydrocarbons.

Answer 5

• Alkanes
• Alkenes
• Alkynes

Question 6

What are alkanes?

Answer 6

• Hydrocarbons containing single carbon-carbon bonds

Question 7

What are alkenes?

Answer 7

• Hydrocarbons that contain at least one carbon-carbon double bond

Question 8

What are alkynes?

Answer 8

• Hydrocarbons that contain at least one carbon-carbon triple bond

Question 9

What is an alkyl group?

Answer 9

• A side chain formed by removing a hydrogen atom from an alkane parent chain
• It has the formula CnH2n+1
• It is often shown as R

Question 10

What is an aryl group?

Answer 10

• A group containing a benzene ring

Question 11

What does the stem of a molecule’s name show?

Answer 11

• The number of carbon atoms in the largest continuous chain

Question 12

What do prefixes show about a molecule?

Answer 12

• The presence of side chains or functional groups

Question 13

What does the suffix of a molecule show?

Answer 13

• Functional groups

Question 14

List the 5 main rules for nomenclature.

Answer 14

1. Identify the suffix
2. Identify the longest continuous chain
3. Number the carbons
4. Identify which number carbon the side chains and functional groups are on
5. Combine the suffix, stem and side chains to name the compound

Question 15

What do you do if there are 2 continuous chains of the same length?

Answer 15

• The one with more branches is the longest

Question 16

Which end do you number the carbons from?

Answer 16

• The side that will give side chains/ functional groups the lowest number
• If the numbers would be the same either way, you give higher priority functional groups the lowest numbers

Question 17

List the 9 main functional groups in order of decreasing priority.

Answer 17

• Carboxylic acids
• Amides
• Aldehydes
• Ketones
• Alcohols
• Alkenes
• Benzene
• Alkanes
• Haloalkanes

Question 18

How do you indicate that there are multiple of the same side chain/ functional group?

Answer 18

• You use the prefixes di, tri and tetra

Question 19

How do you bring the prefixes, suffixes and stems of molecules together?

Answer 19

• You write the side chains/ other functional groups in front of the stem in alphabetic order (ignoring prefixes such as di, tri and tetra)
• You put commas between numbers and dashes between numbers and letters
• If there are 2 suffixes that need to go after the stem, the lower priority one becomes a prefix instead
  Since the stem is mostly the alkane’s name:
• If the stem is followed by a vowel, it loses its e (propanol)
• If it is followed by a consonant, it keeps the e (ethanenitrile)

Question 20

How are alicyclic alkanes named?

Answer 20

• In the same way as alkanes, but the prefix ‘cyclo’ is added
• When a cycloalkane is the shorter chain, it is named like an alkyl group, and the prefix ‘cyclo’ is still used

Question 21

How are haloalkanes named?

Answer 21

• The following prefixes are added:
• chloro
• bromo
• iodo

Question 22

How are alkenes named?

Answer 22

• In the same way way as alkanes, but with the suffix ‘ene’
• If the longest chain has 4 or more carbons, the position of the double bond has to be shown
• Di, tri or tetra are used if there are multiple double bonds
• E.g. but-2-ene/ penta-1,3-diene

Question 23

How are alcohols named?

Answer 23

• With the suffix ‘ol’, and a number before it to show where the hydroxyl group is
• However, if a higher priority functional group is present, it is shown using the prefix ‘hydroxy’ instead

Question 24

What is a ketone?

Answer 24

• Carbon-oxygen double bond (in the middle of a chain), which is known as a carbonyl group

Question 25

How are ketones named?

Answer 25

• With the suffix ‘one’, and the number before it
• If necessary, with the prefix ‘oxo’

Question 26

What are aldehydes?

Answer 26

• They have the functional group CHO (carbon-oxygen double bond)

Question 27

How are aldehydes named?

Answer 27

• With the suffix ‘al’
• A number is not needed as they can only go at the end of a chain, and therefore would be on carbon number 1

Question 28

How are carboxylic acids named?

Answer 28

• With the suffix ‘oic acid’
• They do not need a number as they would always be on carbon 1