4.1 Systematic Nomenclature 1

Definitions Molecular formula Number of atoms in a molecule (element or compound) e.g. C 2 H 4 O 2 Empirical formula Simplest whole number ratio of atoms in a compound e.g. CH 2 O Structural formula Shows the shape and arrangement of atoms in a compound e.g. CH 3 COOH 2

Definitions Structural isomers Same molecular formula but different structural formula e.g. C 2 H 4 O 2 3 Ethanoic AcidMethyl methanoate

Definitions Homologous Series Conform to a general formula Have the same functional group Similar chemical properties Physical properties gradually change 4

Definitions 5 Saturated compounds No multiple bonds between carbon atoms Unsaturated compounds At least one C=C or C ≡ C bond Aromatic compound Contains a benzene ring

Systematic Nomenclature Organic compounds Consist of: Hydrocarbon chain or ring which is non polar and usually unreactive (when saturated) Functional group/s which are involved in chemical reactions and affect physical properties of the compound 6

Naming Organic Compounds No. of carbon atoms Prefix MethEthPropButPentHexHeptOct 7 Find the longest chain of carbons. If there is a functional group it must be attached to one of these carbons.

Naming Organic Compounds No. of branches of same type 234 PrefixDiTriTetra 8 Identify side chains off the main carbon chain. Naming includes number and type of side chains and their position along the main chain. NameMethylEthylPropylButyl Alkyl group CH 3 -C2H5-C2H5-C3H7-C3H7-C4H9-C4H9-

Naming Organic Compounds Homologous series Suffix Alkane-ane Alkene-ene Alkyne-yne Alcohol-ol Aldehyde-al 9 Identify the Functional Group

Naming Organic Compounds Homologous series Suffix Ketone-one Carboxylic acid -oic acid Carboxylate ion -oate ion 10

Naming Organic Compounds Homologous Series Suffix Amine-amine Amide-amide 11

Name the following systematically: 12

4.2 Physical Properties 13

Physical Properties Melting point t m Boiling point t b Solubility in water These properties are affected by the length of the carbon chain and the functional group. 14

Carbon Chains C–C bond is non polar C–H bond is virtually non polar Tetrahedral symmetry around each carbon results in carbon chains being non polar. Polarity of a carbon compound is determined by the polarity of the functional group/s 15

Alkanes 16 Non polar molecules Secondary forces are Dispersion forces Low t m /t b As chain length increases (molar mass increases).  Dispersion forces increase.

Aldehydes 17 Polar functional group Secondary forces are dipole- dipole interactions t m /t b higher than corresponding alkane

Aldehydes Effect of the functional group on t b decreases as the carbon chain length increases 18

Alcohols 19 Polar functional group Secondary forces are Hydrogen bonds t m /t b are higher than the corresponding alkane or aldehyde

Alcohols Effect of the functional group on t b decreases as the carbon chain length increases 20

Carboxylic acids 21 Very polar functional group Secondary forces are Hydrogen bonds t m /t b are higher than the corresponding alkane or aldehyde or alcohol

Other Polar Functional Groups 22 Amines: Hydrogen bonds Ketones and Esters: Dipole-dipole interactions

Effect of functional group on T b 23 Propanoic acid: 141 o C Methyl ethanoate: 57 o C Ethyl methanoate: 55 o C

Solubility “Like dissolves like” To determine the solubility of organic compounds consider: The number and types of functional groups (Identify the secondary bonding) The size/ length of the non polar carbon chain 24

Solubility in water To be soluble in water an organic compound must Hydrogen bond with the water. As the carbon chain increases the solubility decreases 25

4.3 Alcohols 26

Alcohols Ethanol production 80% from fermentation of glucose C 6 H 12 O 6 which is a monosaccharide. The glucose is obtained directly from fruits (e.g. grapes) or from the hydrolysis of disaccharides or polysaccharides (starch) from vegetables and grains. 27

Hydrolysis (C 6 H 10 O 5 ) n +½nH 2 O  ½nC 12 H 22 O 11 polysaccharide disaccharide C 12 H 22 O 11 + H 2 O  2C 6 H 12 O 6 disaccharide monosaccharide Overall (C 6 H 10 O 5 ) n +nH 2 O  nC 6 H 12 O 6 28

Ethanol production C 6 H 12 O 6  2C 2 H 5 OH +CO 2  H=  ve Conditions Presence of yeast Temperature of o C which is maintained so the enzymes in the yeast catalyse the reaction. Almost complete absence of oxygen. Small amount required for yeast metabolism but too much will oxidise the alcohol 29

Alcohols 30 Primary alcohol Secondary alcohol Tertiary alcohol

Oxidation of Alcohols Primary and secondary alcohols can be oxidised by an oxidising agent like acidified dichromate Cr 2 O 7 2–  Cr 3+ orange green Tertiary alcohols are NOT oxidised by dichromate ions. This reaction and the products formed can be used to identify the type of alcohol present 31

Oxidation of Alcohols Primary alcohols Oxidised to the corresponding aldehyde and then carboxylic acid 32

Oxidation of Alcohols Secondary alcohols Oxidised to the corresponding ketone 33

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