More on alcohols
- Created by: Emily Cartwright
- Created on: 25-05-14 19:54
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- More on alcohols
- Alcohols are classified by counting how many other carbon atoms are bonded to the carbon that bears the -OH group
- A primary alcohol is one in which the carbon atom joined to the OH group is also bonded to 1 other carbon atom
- The general formula of a primary alcohol is RCH2OH
- A secondary alcohol is one in which the carbon atom joined to the OH is also bonded to 2 other carbon atoms
- The general formula of a secondary alcohol is R2CHOH
- A tertiary alcohol is one in which the carbon atom joined to the OH is also bonded to three other carbon atoms
- The general formula of a tertiary alcohol is R3COH
- A primary alcohol is one in which the carbon atom joined to the OH group is also bonded to 1 other carbon atom
- Oxidation and Reduction
- Oxidation involves the gain of one or more oxygen atoms and/or the loss of one or more hydrogen atoms
- Reduction involves the gain of one or more hydrogen atoms and/or the loss of one or more oxygen atoms
- Oxidation of alcohols
- The oxidising agent used to convert alcohols to other organic compounds is hot aqueous acidic potassium dichromate (K2Cr2O7)
- The colour change when an alcohol is oxidised by hot aqueous acidic potassium dichromate is orange to green
- The outcome of treatment with hot aqueous acidic potassium dichromate is different for primary, secondary and tertiary alcohols;
- A primary alcohol is oxidised in two stages
- First, it loses two hydrogen's to form a compound called an aldehyde
- These reactions are performed by heating the alcohol briefly with aqueous acidic potassium dichromate
- If the heating is carried out for a long time with excess oxidising agent, the aldehyde can be oxidised furthur to form an carboxylic acid
- These reactions are performed by heating the alcohol briefly with aqueous acidic potassium dichromate
- First, it loses two hydrogen's to form a compound called an aldehyde
- Secondary alcohols are oxidised to ketones, which are not oxidised furthur
- Ketones are named with the root name indicating the structure of the carbon skeleton and the ending -one
- Tertiary alcohols are not oxidised by hot, aqueous acidic potassium dichromate
- A primary alcohol is oxidised in two stages
- Controlling the products of oxidation
- Distillation
- This method is used to make aldehydes from primary alcohols
- It works by boiling the aldehyde away as soon as it is formed, and condensing it elsewhere, away from the oxidising agent so furthur oxidation does not occur
- This method is used to make aldehydes from primary alcohols
- Refluxing
- This method is used to make; carboxylic acids from primary alcohols and ketones from secondary alcohols
- It involves a continuous cycle of boiling, condensing and return to the reaction flask
- It ensures that the reaction can continue for a long time with the oxidising agent while avoiding losing material through evaporation
- This helps ensure:
- A good yield of product if the reaction is slow
- Oxidation of a primary alcohol through both stages to the carboxylic acid
- At the end of refluxing the product can be purified from the reaction mixture by distillation
- This helps ensure:
- It ensures that the reaction can continue for a long time with the oxidising agent while avoiding losing material through evaporation
- It involves a continuous cycle of boiling, condensing and return to the reaction flask
- This method is used to make; carboxylic acids from primary alcohols and ketones from secondary alcohols
- Distillation
- Alcohols are classified by counting how many other carbon atoms are bonded to the carbon that bears the -OH group
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