Draw the first 4 member of alkane

serie

Are saturated aliphatic hydrocarbons

Each molecule differs from the next by

the structural unit –CH2–

This is a homologous series – when each

member increases by the same structural

unit

The general formula for an alkane is

CnH2n+2

Using the general formula for an alkane, derive the following for specific alkanes. › A) number of H atoms present when 8

carbon atoms are present.

› B) Number of C atoms present when 10 hydrogen atoms are present.

› C) Number of C atoms present when 41 total atoms are present.

› D) The total number of covalent bonds present in the molecule when 7 carbon atoms are present.

Further practice problems

Worksheet 1 – problems number 13 - 16

Non-polar

Thus are soluble in non-polar solvents

and not soluble in polar solvents

Remember: Like Dissolves Like

Have relatively low boiling points

Boiling points, melting points and

densities of straight-chain alkanes

increase with increasing chain length

The strength of London dispersion forces between molecules increase with increasing length of carbon chain

Review: your notes or click on the following link: http://www.chem.purdue.edu/gchelp/liquids/disperse.html

Carbons bonded together in long,

continuous, chain-like structures

Also called unbranched alkanes

Ex.

All alkanes end with the suffix –ane

Root of the name is based on the

number of carbons in the chain

Examples: Methane 1 Carbon

Ethane 2 Carbons

# of C

Atoms Root IUPAC name

Condensed Structural

Formula

1 Meth- Methane CH4

2 Eth- Ethane CH3―CH3

3 Prop- Prapane CH3―CH2―CH3

4 But- Butane

5 Pent-

6 Hex-

7 Hept-

8 Oct-

9 Non-

10 Dec-

# of C

Atoms Root IUPAC name Condensed Structural Formula

1 Meth- Methane CH4

2 Eth- Ethane CH3―CH3

3 Prop- Prapane CH3―CH2―CH3

4 But- Butane CH3―CH2―CH2―CH3

5 Pent- Pentane CH3―CH2―CH2―CH2―CH3

6 Hex- Hexane CH3―CH2―CH2―CH2―CH2―CH3

7 Hept- Heptane CH3―CH2―CH2―CH2―CH2―CH2―CH3

8 Oct- Octane CH3―CH2―CH2―CH2―CH2―CH2―CH2―CH3

9 Non- Nonane CH3―CH2―CH2―CH2―CH2―CH2―CH2―CH2―CH3

10 Dec- Decane CH3―CH2―CH2―CH2―CH2―CH2―CH2―CH2―CH2―CH3

What is the name of this compound?

CH3—CH2—CH2—CH2—CH3

Ex.

Branches are sometimes called side

chains.

The side chains originating in alkanes

are called alkyl groups.

What is the general formula for

branched-chain alkanes?

We name these based on their parent

chain (longest chain) and side chains

Naming follows the general formula:

Prefix + Root + Suffix

Root: the longest continuous chain in

the hydrocarbon (the parent chain)

Suffix: for all alkanes, the suffix is –ane

Prefix: the branches attached to the

parent chain

Alkyl groups are alkanes with one less

hydrogen

Naming:

Root (# of C in a side chain) + suffix - yl

Eg. Alkane: Propane CH3CH2CH3

Alkyl Group: Propyl CH3CH2CH2 ――

Numbers

of

Carbon

IUPAC Root IUPAC name

of the alkyl

group

Condensed structural formula

1 Meth- Methyl CH3 ―

2 Eth- Ethyl

3 Prop-

4

Numbers

of

Carbon

IUPAC Root IUPAC name

of the alkyl

group

Condensed structural formula

1 Meth- Methyl CH3 ―

2 Eth- Ethyl CH3 ― CH2 ―

3 Prop- Propyl CH3 ― CH2 ― CH2 ―

4 But- Butyl CH3 ―CH2 ― CH2 ― CH2 ―

Prefixes are numbered based on their position along the parent chain – these numbers are always given so that the branch has the lowest possible number!

When putting prefixes together in the name: › Prefixes are put in alphabetical order

› If there are two or more of the same type of branch, use multiplying prefixes (di, tri etc)

› Position numbers are put in ascending order

› Hyphens separate numbers from words

› Commas separate numbers

1. Locate the parent alkane (this is the

longest chain) and name it (root and suffix

-ane)

2. Assign position numbers: number the

parent chain starting with the end closest

to the branch

3. Identify prefixes: name the branches

4. Put it together!

Prefix + Root + Suffix

CH3 ― CH2 ― CH2 ― CH ― CH3

І

CH3

CH3 ― CH ― CH2 ― CH2― CH3

І

CH2 ― CH3

CH3 ― CH ― CH2 ― CH ― CH3

І І

CH3 CH3

CH3

І

CH3 ― CH2 ― C ― CH2 ― CH3

І

CH3

CH3 ― CH2 ― CH ― CH ― CH3 І І CH2 CH3 І CH3

CH3 ― CH2 ― CH ― CH ― CH ― CH2 ― CH2 ―CH3 І І І CH2 CH2 CH2

І І І CH3 CH2 CH2 І І CH3 CH3

Naming alkanes

Worksheet 1 – problems number 17 – 19

Worksheet 2 – problem number 1

Draw a condensed structural formula for

2,3-dimethylhexane

Step 1: Identify the root and the suffix of

the name.

Hexane.

The name tells you that this hydrocarbon

contains 6 carbon atoms (root: hex-) and

it contains only single carbon-carbon

bonds (suffix: -ane).

Step 2: Draw the skeletal structure for

hexane (only carbons, no hydrogens).

Leave spaces beside each carbon on

the main chain to write the number of

hydrogen atoms later.

Step 3: Number the carbons in the main

chain.

Step 4: Complete the carbon skeleton by

attaching alkyl groups as they are

specified in the name. Add one methyl

group to carbon 2 and second to

carbon 3.

Step 5: Add hydrogen atoms to the carbon skeleton so that each carbon atom has four bonds.

CH3 ― CH ― CH ― CH2 ― CH3

І І

CH3 CH3

Draw a condensed structural formula for:

a) 3-ethyl-2-methylheptane

b) 4,5-diethyl-3,4,5-trimethyloctane.

3-ethyl-2-methylheptane

CH2 ― CH3

І

CH3 ― CH ― CH ― CH2 ― CH2 ― CH2 ― CH3 І

CH3

4,5-diethyl-3,4,5-trimethyloctane

CH3 CH3

І І

CH2 CH2

І І

CH3 ― CH2 ― CH ― C ― C ― CH2 ― CH2 ― CH3 І І І

CH3 CH3 CH3

Drawing alkanes:

Worksheet 1 – problem 20

Worksheet 2 – problems 2-7

• Worksheet 1 – problems number 13 – 16

• Worksheet 1 – problems number 17 – 19

• Worksheet 2 – problem number 1

• Worksheet 1 – problem 20

• Worksheet 2 – problems 2-7