CHAPTER 16 HYDROXY COMPOUNDS

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CHAPTER 16 HYDROXY COMPOUNDS
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LEARNING OUTCOMES

• Give the general formula of alcohol.
• Draw the structures, classify and name the
  hydroxy compounds (C1 C10) according to the
  IUPAC nomenclature (include phenols).
• Explain the physical properties
• boiling point
• solubility

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Introduction

• The hydroxyl group (-OH) functional group
• 2 types of hydroxy compounds - aliphatic alcohol
  aromatic alcohol (phenol)

Video 1
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• Aliphatic alcohol
• CnH2n1OH
• OH attached to alkyl group, R
• IUPAC nomenclature
• e (alkane) ol (alcohol)
• eg -
• CH3CH2OH ethanol
• CH3CH2CH2OH propanol

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Classification of alcohols

• 1,2 3 alcohols
• primary alcohol (1) OH group attached to 1
  carbon (eg CH3CH2OH - ethanol)
• secondary alcohol (2) OH group attached to 2
  carbon (eg 2-butanol)
• tertiary alcohol (3) OH group attached to 3
  carbon (2-methyl-2-propanol)

Video 2
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Nomenclature of Alcohol

• Aliphatic alcohol
• ? The parent alcohol - the longest C chain with
  OH group attached to it
• ? OH group is given the lowest number in the
  chain.
• ? prefix suffix used if alkyl groups are
  exist more than one times

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2- butanol
4,4-dimethyl-2-pentanol
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3-pentanol
cyclopentanol
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• When there are two or more OH groups present,
  the name ends with diol, triol and so on.

2,4-pentanediol
1,2,2-propanetriol
Video 3
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• Aromatic alcohol (phenols)
• In most cases, the name phenol is used as the
  parents name.

4-methylphenols
3-nitrophenols
(4-methyl hydroxybenzene)
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Physical Properties of Alcohol

• Boiling point

• The boiling point of an alcohol is always much
  higher than that of the alkane with the same
  number of carbon atoms.
• Intermolecular foces
• Between alkanes, the presence of van der Waals
  forces.
• Between alcohols, the presence of hydrogen
  bonding
• Hydrogen bonding are much stronger than VdW
  forces and therefore it takes more energy to
  separate alcohol molecules than it does to
  separate alkane molecules.
• Therefore, boiling point of alcohols is higher
  than alkanes.

Video 4
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• The boiling points of the alcohols increase as
  the number of carbon atoms increases.
• Alcohols with lower number of carbons has smaller
  size compared to alcohols with higher number of
  carbons.
• Alcohols with smaller size will have weaker van
  der Waals forces instead of hydrogen bonding that
  is formed between OH group.
• Therefore, alcohols with lower number of carbons
  have lower boiling points.

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• (ii) Solubility
• The lower alcohols (eg - methanol, ethanol,
  propanol and tert-butyl alcohol) are completely
  miscible with water.
• Because of hydrogen bonding between a water
  molecule and a alcohol molecule.

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As the alkane-like alkyl group (hydrophobic _at_
water hating) becomes larger, water solubility
decrease.
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Exercise

• Give the structure of
• a) 3-ethyl-2-methyl-1-hexanol
• b) 3-cyclohexyl-2-methyl-2-butanol
• c) 3-methyl-3-hexanol
• d) 4-methyl-3-phenyl-2-hexanol
• e) 1-ethylcyclohexanol