CARBON CHEMISTRY

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CARBON CHEMISTRY

• Dr. Fazlul Huq
• School of Biomedical Sciences
• The University of Sydney

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What are organic compounds?

• Compounds of carbon with other elements such as
  H, N, Cl, P, Br and I
• Most matter in living systems are composed of
  organic compounds
• Some metals such as iron, copper, zinc and cobalt
  are also found as parts of organic molecules
  present in biological systems

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Different Classes of Organic Compounds

• Hydrocarbons - composed of C and H only
• Alcohols - RCH2OH
• Aldehydes - RCHO
• Carboxylic acids - RCOOH
• Esters - RCOOR
• Ethers - ROR
• Amines - RNH2

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What are hydrocarbons?

• Compounds of carbon and hydrogen only. For
  example, methane (CH4), ethane (C2H6)
• Different classes of hydrocabons include
• Alkanes
• Alkenes
• Alkynes
• Cycloalkanes
• Arenes

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Saturated Carbon

• Saturated carbon
• bonded to 4 atoms
• tetrahedral geometry

109.5o
C
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Unsaturated Carbon

• Involved in double or triple bonds

C C C C
Geometry is triangular
Geometry is linear
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First Seven Alkanes
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Properties of Alkanes

• As the number of C atoms present in the molecule
  increases, mp and bp increase
• eg CH4 is a gas whereas C6H14 is a liquid
• Non-polar and hence insoluble in water but
  soluble in kerosene
• Undergo substitution and combustion reactions

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Naming of Alkanes

• Find the longest carbon chain
• Circle the substituents
• Number the carbon chain so as to give smallest
  numbers to substituents.
• Some substituents
• CH3- is methyl
• CH3CH2- is ethyl
• CH3CH2CH(CH3)CH3 is 2-methylbutane

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Examples
CH3
CH3CH2CH2CHCH2CH2CH3 is 3-methylheptane
1 2 3 4 5 6 7
CH3
CH3CCH3 is 2,2-dimethylpropane
CH3
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What are isomers?

• Different compounds with the same molecular
  formula but with different structures (ie
  different arrangement of atoms in the molecule)
• eg butane and 2-methylpropane are isomers

CH3CH2CH2CH3 CH3CHCH3
CH3
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Alkenes

• Hydrocarbons having a CC bond
• eg CH2CH2 which is called ethene
• Names of alkenes end in ene
• Can have cis- and trans-isomers

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Naming of Alkenes

• Find the longest carbon chain containing the CC
  bond
• Number the carbon chain so as to give the
  smallest possible number to the double bond

is 1-butene
CH3CH2CHCH2
is 2-butene
CH3CHCHCH3
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Cis- and Trans-isomers

• Geometrical isomers having the same linkage of
  atoms but with different arrangements of atoms in
  space
• Cis- means on the same side and trans- means on
  the opposite side
• eg cis-2-butene and trans-2-butene

H
CH3
CH3
CH3
CC
CC
H
H
CH3
H
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Functional Group

• Common structural feature present in a class of
  organic compounds such as alkenes, alcohols,
  carboxylic acids, etc.
• Determines to a great extent the properties of
  the class of compounds
• eg the functional group of alkenes is

CC
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Some Functional groups
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Alcohols

• Organic compounds containing the functional group
  -OH bonded to carbon
• -OH is a polar group and hence alcohols are polar
• Alcohols with a small number of carbon atoms are
  soluble in water
• since they can form H-bonds with water
• As the number of carbon atoms present in an
  alcohol increases, polarity of the molecule
  decreases and hence solubility in water also
  decreases
• eg CH3(CH2)10CH2OH is insoluble in water

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Naming of alcohols

• Names in ol
• eg CH3CH2OH is called ethanol
• CH3CH2CH2OH is called 1-propanol
• CH3CH(OH)CH3 is called 2-propanol

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Carboxylic acids

• Organic compounds containing the functional group
  -COOH
• Names end in oic
• eg CH3COOH is ethanoic acid
• CH3CH2COOH is propanoic acid
• -COOH, more exactly C

O
O H
is polar
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Solubility of Carboxylic Acids

• Carboxylic acids are polar
• Polarity decreases as the number of carbon atoms
  present in the molecule increases
• Carboxylic acids with a small number of C atoms
  are soluble in water but insoluble in kerosene
  and those with a a large number of C atoms are
  insoluble in water but soluble in kerosene
• CH3COOH is soluble in water but insoluble in
  kerosene
• CH3(CH2)10COOH is insoluble in water but soluble
  in kerosene

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Fatty Acids

• Carboxylic acids with a long carbon chain
• Insoluble in water but soluble in kerosene
• CH3(CH2)16COOH is a fatty acid which is insoluble
  in water but soluble in kerosene
• Unsaturated fatty acids have one or more CC
  bonds
• Unsaturated fatty acids present in biological
  systems are often found in cis-conformation which
  is more bent than trans-conformation
• Cis- is V-shaped whereas trans- is straighter

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Esters

• Condensation products of carboxylic acids and
  alcohols
• Names have two parts
• CH3CH2OOCCH2CH3 is ethyl propanoate
• Esters are insoluble in water since polar groups
  present in the interior are shielded by non-polar
  on the outside