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Alcohol reactions

Alcohol reactions. Alcohols – reactions. Addition of alkene to form alcohol. Elimination of alcohol to form alkene. Halogenation (substitution) of alcohol to form haloalkane. Oxidation of alcohol to form aldehyde/ketone and carboxylic acid. Alkene to alcohol.

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Alcohol reactions

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  1. Alcohol reactions

  2. Alcohols – reactions • Addition of alkene to form alcohol. • Elimination of alcohol to form alkene. • Halogenation (substitution) of alcohol to form haloalkane. • Oxidation of alcohol to form aldehyde/ketone and carboxylic acid.

  3. Alkene to alcohol • Addition – Adding water to alkene gives an alcohol. • this occurs when we heat the alcohol with 50% sulfuric acid. • The hydrogen and the OH of the water is added to the alkene around the double bond.

  4. Alcohol to alkene • Elimination – removing water from an alcohol produces an alkene (by conc H2SO4) • The removal of 2 atoms or groups is known as an elimination reaction • The –OH and hydrogen from the neighbouring atom are removed.

  5. Alcohol and oxygen • Combustion: Alcohol of low molar mass burn easily in the presence of oxygen, to form carbon dioxide and water.

  6. Alcohols - Elimination • Or dehydration –removal of the hydroxyl group and hydrogen atom of the neighbouring carbon • concH2SO4/heat CH3CH(OH)CH3 CH3CH=CH2 + H2O propan-2-ol propene

  7. Alcohols – Halogenation (substitution)

  8. Alcohols - substitution • Or halogenation: –OH replaced by halogen atom forms a haloalkane • PCl5 – phosphorus pentachloride • SOCl2 – thionyl chloride (These things put chloride on and kick off –OH group) • Performed under reflux – increases the rate of substitution • These can be used to substitute the –OH group in an alcohol with a –Cl: CH3OH + PCl5 CH3Cl+ POCl3 + HCl CH3OH + SOCl2 CH3Cl+ SO2 + HCl

  9. Lucas reagent • Lucas reagent – anhydrous Zinc chloride (ZnCl2) and conc HCl. • The Lucas reagent is used to primary, secondary and tertiary alcohols • The zinc chloride is a catalyst for the substitution reaction between the alcohol and HCl. • The chloroalkane (haloalkane) formed is a cloudy suspension in water as they are insoluble. • The rates at which different alcohols react make it possible to classify them.

  10. Alcohols - Substitution

  11. Alcohols - Oxidation • Back in Level 2 organic chemistry we learnt that alcohols come in three main forms: • Primary • Secondary • Tertiary • We also found out that primary alcohols can be oxidised to form carboxylic acids • Later we will discover that primary alcohols can be partially oxidised to form a group called aldehydes. Then the aldehydes can be oxidised further to form carboxylic acids: • This year we will also discover that secondary alcohols can be oxidised to form ketones:

  12. Alcohols - Oxidation

  13. Alcohols - Oxidation

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