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Organic and Biological Chemistry

Organic and Biological Chemistry . 4.1 Systematic Nomenclature. 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

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Organic and Biological Chemistry

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  1. Organic and Biological Chemistry 4.1 Systematic Nomenclature

  2. Definitions Molecular formula • Number of atoms in a molecule (element or compound) e.g. C2H4O2 Empirical formula • Simplest whole number ratio of atoms in a compound e.g. CH2O Structural formula • Shows the shape and arrangement of atoms in a compound e.g. CH3COOH

  3. Definitions Structural isomers • Same molecular formula but different structural formula • e.g. C2H4O2 Ethanoic Acid Methyl methanoate

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

  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 Definitions

  6. 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

  7. Naming Organic Compounds Find the longest chain of carbons. If there is a functional group it must be attached to one of these carbons.

  8. Naming Organic Compounds Identify side chains off the main carbon chain. Naming includes number and type of side chains and their position along the main chain.

  9. Naming Organic Compounds Identify the Functional Group

  10. Naming Organic Compounds

  11. Naming Organic Compounds

  12. Name the following systematically:

  13. Organic and Biological Chemistry 4.2 Physical Properties

  14. Physical Properties • Melting point tm • Boiling point tb • Solubility in water • These properties are affected by the length of the carbon chain and the functional group.

  15. 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

  16. Alkanes • Non polar molecules • Secondary forces are Dispersion forces • Low tm/tb • As chain length increases (molar mass increases). Dispersion forces increase.

  17. Aldehydes • Polar functional group • Secondary forces are dipole-dipole interactions • tm/tb higher than corresponding alkane

  18. Aldehydes • Effect of the functional group on tb decreases as the carbon chain length increases

  19. Alcohols • Polar functional group • Secondary forces are Hydrogen bonds • tm/tb are higher than the corresponding alkane or aldehyde

  20. Alcohols • Effect of the functional group on tb decreases as the carbon chain length increases

  21. Carboxylic acids • Very polar functional group • Secondary forces are Hydrogen bonds • tm/tb are higher than the corresponding alkane or aldehyde or alcohol

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

  23. Effect of functional group on Tb • Propanoic acid: 141oC • Methyl ethanoate: 57oC • Ethyl methanoate: 55oC

  24. 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

  25. 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

  26. Organic and Biological Chemistry 4.3 Alcohols

  27. Alcohols Ethanol production • 80% from fermentation of glucose C6H12O6 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.

  28. Hydrolysis • (C6H10O5)n +½nH2O ½nC12H22O11 polysaccharide disaccharide • C12H22O11 + H2O  2C6H12O6 disaccharide monosaccharide • Overall • (C6H10O5)n +nH2O  nC6H12O6

  29. Ethanol production • C6H12O62C2H5OH +CO2 H=ve Conditions • Presence of yeast • Temperature of 20-30oC 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

  30. Alcohols • Primary alcohol • Secondary alcohol • Tertiary alcohol

  31. Oxidation of Alcohols • Primary and secondary alcohols can be oxidised by an oxidising agent like acidified dichromate • Cr2O72– Cr3+ 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

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

  33. Oxidation of Alcohols Secondary alcohols • Oxidised to the corresponding ketone

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