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Organic and Biological Chemistry 4.1 Systematic Nomenclature1

Stage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.37/06/20121DefinitionsMolecular formulaNumber of atoms in a molecule (element or compound) e.g. C2H4O2Empirical formulaSimplest whole number ratio of atoms in a compound e.g. CH2OStructural formulaShows the shape and arrangement of atoms in a compound e.g. CH3COOH2Stage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.327/06/2012DefinitionsStructural isomersSame molecular formula but different structural formulae.g. C2H4O23

Ethanoic AcidMethyl methanoateStage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.337/06/2012DefinitionsHomologous SeriesConform to a general formulaHave the same functional groupSimilar chemical propertiesPhysical properties gradually change

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Stage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.37/06/20124Definitions

5Saturated compoundsNo multiple bonds between carbon atomsUnsaturated compoundsAt least one C=C or CC bondAromatic compoundContains a benzene ring

Stage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.357/06/2012Systematic NomenclatureOrganic compoundsConsist 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

6Stage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.367/06/2012Naming Organic CompoundsNo. of carbon atoms12345678PrefixMethEthPropButPentHexHeptOct7Find the longest chain of carbons. If there is a functional group it must be attached to one of these carbons.

Stage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.377/06/2012Naming Organic CompoundsNo. of branches of same type234PrefixDiTriTetra8Identify side chains off the main carbon chain. Naming includes number and type of side chains and their position along the main chain.NameMethylEthylPropylButylAlkyl groupCH3-C2H5-C3H7-C4H9-Stage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.387/06/2012Naming Organic CompoundsHomologous seriesSuffixAlkane-aneAlkene-eneAlkyne-yneAlcohol-olAldehyde-al

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Identify the Functional GroupStage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.397/06/2012Naming Organic CompoundsHomologous seriesSuffixKetone-oneCarboxylic acid-oic acidCarboxylate ion-oate ion

10Stage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.3107/06/2012Naming Organic CompoundsHomologous SeriesSuffixAmine-amineAmide-amide

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Stage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.3117/06/2012Name the following systematically:12

Stage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.3127/06/2012Organic and Biological Chemistry 4.2 Physical Properties

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Physical PropertiesMelting point tm

Boiling point tb

Solubility in water

These properties are affected by the length of the carbon chain and the functional group.14

Stage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.3147/06/2012Carbon ChainsCC bond is non polarCH bond is virtually non polarTetrahedral 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/s15

Stage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.3157/06/2012Alkanes

16Non polar moleculesSecondary forces are Dispersion forcesLow tm/tbAs chain length increases (molar mass increases). Dispersion forces increase.Stage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.3167/06/2012Aldehydes17

Polar functional groupSecondary forces are dipole-dipole interactionstm/tb higher than corresponding alkaneStage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.3177/06/2012AldehydesEffect of the functional group on tb decreases as the carbon chain length increases18

Stage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.3187/06/2012Alcohols19

Polar functional groupSecondary forces are Hydrogen bondstm/tb are higher than the corresponding alkane or aldehydeStage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.3197/06/2012AlcoholsEffect of the functional group on tb decreases as the carbon chain length increases20

Stage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.3207/06/2012Carboxylic acids21

Very polar functional groupSecondary forces are Hydrogen bondstm/tb are higher than the corresponding alkane or aldehyde or alcoholStage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.3217/06/2012Other Polar Functional Groups22

Amines: Hydrogen bondsKetones and Esters: Dipole-dipole interactionsStage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.3227/06/2012Effect of functional group on Tb23

Propanoic acid: 141oC

Methyl ethanoate: 57oC

Ethyl methanoate: 55oCStage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.3237/06/2012SolubilityLike dissolves likeTo 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 chain24

Stage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.3247/06/2012Solubility in waterTo be soluble in water an organic compound must Hydrogen bond with the water.As the carbon chain increases the solubility decreases 25

Stage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.3257/06/2012Organic and Biological Chemistry 4.3 Alcohols

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AlcoholsEthanol production80% 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.27

Stage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.3277/06/2012Hydrolysis(C6H10O5)n +nH2O nC12H22O11 polysaccharide disaccharideC12H22O11 + H2O 2C6H12O6 disaccharide monosaccharide

Overall(C6H10O5)n +nH2O nC6H12O6

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Stage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.3287/06/2012Ethanol productionC6H12O6 2C2H5OH +CO2 H=veConditionsPresence of yeastTemperature 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 29

Stage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.3297/06/2012Alcohols30

Primary alcoholSecondary alcoholTertiary alcohol

Stage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.3307/06/2012Oxidation of AlcoholsPrimary and secondary alcohols can be oxidised by an oxidising agent like acidified dichromateCr2O72 Cr3+ orange greenTertiary alcohols are NOT oxidised by dichromate ions.This reaction and the products formed can be used to identify the type of alcohol present31

Stage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.3317/06/2012Oxidation of AlcoholsPrimary alcoholsOxidised to the corresponding aldehyde and then carboxylic acid32

Stage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.3327/06/2012Oxidation of AlcoholsSecondary alcoholsOxidised to the corresponding ketone33

Stage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.3337/06/201234

Stage 2 Chemistry Lecture 14: Topics 4.1, 4.2, 4.37/06/201234AlkaneCH4C2H6C3H8C4H10C5H12

Tb oC-162-89-42-0.536

AldehydeCH2OC2H4OC3H6OC4H8OC5H10O

Tb oC-19204875103

Alkane-162-89-42-0.5

Aldehyde-19204875

Difference1431099075.5

AlcoholCH3OHC2H4OHC3H7OHC4H9OHC5H11OH

Tb oC657897118138

Alkane-162-89-42-0.5

Alcohol657897118

Difference227167139118.5

AcidCH2O2C2H4O2C3H6O2C4H8O2C5H10O2

Tb oC101118141163186