Organic Families

8/4/2019 Organic Families

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GROUPS OF ORGANIC

COMPOUNDS


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ORGANIC COMPOUNDS

HYDROCARBONS - COMPOUNDS of CARBONand HYDROGEN only.

AROMATIC

HYDROCARBONSwhich have benzene ring

structures with double

bonds

ALIPHATIC

HYDROCARBONS

straight chain structures

ALKANES single bonds

ALKENES double bonds

ALKYNES triple bonds

Can be

Can be either


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Some terminology:

Saturated hydrocarbons these molecules

have only single bonds between carbon

atoms.

Unsaturated hydrocarbons

Those compounds with double and triplebonds between carbon atoms are said to be

unsaturated.


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A homologous series is a family of

compounds where each member differs

from the previous one by a CH2 group.

Functional groups are small structural units

within molecules at which most of the

chemical reactions occur. The functionalgroup determines the chemical properties of

the molecule.


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Hydrocarbons can be represented by:

a molecular formula C2H6

a condensed structural formulaCH3CH3

a structural formula


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ALKANES

The carbon atoms are joined to each other by

single bonds. Each C atom makes 4 covalent

bonds and so all other bonds are to hydrogen

atoms.

Methane CH4 Ethane C2H6Propane C3H8


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Alkane

name

No

of C

Molecular

Formula

Condensed structural formula

Methane 1 CH4 CH4

Ethane 2 C2H6 CH3CH3

Propane 3 C3

H8 CH3CH2CH3

Butane 4 C4H10 CH3 CH2CH2CH3

Pentane 5 C5H12 CH3 CH2 CH2CH2CH3

Hexane 6 C6H14 CH3 CH2 CH 2CH2CH2CH3

Heptane 7 C7H16 CH3 CH2 CH2CH 2CH2CH2CH3

Octane 8 C8H18 CH3 CH 2CH2 CH2CH 2CH2CH2CH3

Nonane 9 C9H20 CH3 CH 2CH2 CH 2CH2CH 2CH2CH2CH3

THE ALKANE HOMOLOGOUS SERIES

Decane 10 C 10H22 CH3CH2CH 2CH2CH 2CH2CH 2CH2CH2CH3


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Create a similar table for the alkenes.

Replace one of the C C bonds with a

double C=C bond.

Create a similar table for the alkynes.

Replace one of the C C bonds with a

triple C-C bond.

Draw structural formulae for each molecule

represented in the tables.

FOR YOU TO DO:


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Hydrocarbon General

FormulaAlkane CnH2n

Alkene CnH2n +2

Alkyne CnH2n - 2

Distinguish between the hydrocarbons

using the general formulae


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Straight and branched chain hydrocarbons:

The hydrocarbons represented in the tablegiven in the previous slide are all STRAIGHT

chain hydrocarbons.

Carbon chains can be branched whichmeans that one of the hydrogen atoms is

replaced by an alkyl group.

2 methylbutane


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Alkyl group

structure

Alkyl name

CH3 - methyl

CH3CH2- ethyl

CH3CH2CH2 - propyl

CH3CH2 CH2CH2 - butyl

Naming alkyl groups


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FUNCTIONAL GROUPS


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RULES FOR NAMING ORGANIC

COMPOUNDS (IUPAC RULES)

Identify the functional group of the molecule

this determines the ending of the name.

Eg only single bonds ends in -ane

Find the longest continuous carbon chain and

allocate its prefix according to the number ofcarbon atoms in the chain (see table for

prefixes).


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Name the branched group according to the

number of carbon atoms it has and give it anumber according to the carbon atom it is

attached to.

Number the carbon atoms in the chain.

Number them so that the functional group is

on the carbon of lowest possible number.

Double and triple bonds take preference over

side chains.


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No of C atoms Prefix

1 Meth

2 eth -

3 prop -

4 but -

5 pent -

6 hex -

7 hept -8 oct -

9 non -

10 dec -

Name prefixes


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If there is more than one branched group of

the same kind, use the Greek prefixes di,

tri, tetra, penta and so on to indicate this.

If a halogen atom is attached to the carbonchain, it is treated as an alkyl group.

The prefixes: fluoro-, chloro-, bromo -, and

iodo are used.

eg tetra-chloro methane CCl4


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For alcohols, the name ending ol is used.

eg ethanol.

For carboxylic acids, the name ending

oic acid is used.

eg ethanoic acid.


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Longest chain 4 carbon atoms = prefix but

Functional group alkane = name ends -ane

Alkyl group on C2 = 2-methyl

Apply the rules:


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Name:

2-methyl butane

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