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Published byEugene Doyle Modified over 9 years ago
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Alcohol reactions
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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.
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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.
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Alcohol to alkene Elimination – removing water from an alcohol produces an alkene (by conc H 2 SO 4 ) The removal of 2 atoms or groups is known as an elimination reaction The –OH and hydrogen from the neighbouring atom are removed.
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Alcohol and oxygen Combustion: Alcohol of low molar mass burn easily in the presence of oxygen, to form carbon dioxide and water.
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Alcohols - Elimination Or dehydration –removal of the hydroxyl group and hydrogen atom of the neighbouring carbon conc H 2 SO 4 /heat CH 3 CH(OH)CH 3 CH 3 CH=CH 2 + H 2 O propan-2-ol propene
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Alcohols – Halogenation (substitution)
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Alcohols - substitution Or halogenation: –OH replaced by halogen atom forms a haloalkane –PCl 5 – phosphorus pentachloride –SOCl 2 – 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: CH 3 OH + PCl 5 CH 3 Cl + POCl 3 + HCl CH 3 OH + SOCl 2 CH 3 Cl + SO 2 + HCl
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Lucas reagent Lucas reagent – anhydrous Zinc chloride (ZnCl 2 ) 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.
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Alcohols - Substitution
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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:
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Alcohols - Oxidation
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