Organic synthesis
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Identify the functional groups present in the following molecule: CH3CH2COCH2CH=CH2
The molecule contains a ketone (C=O) and an alkene (C=C) functional group.
Name the reagents and conditions required to reduce a carboxylic acid to a primary alcohol.
The reagent required is Lithium Aluminium Hydride (LiAlH₄) in dry ether, followed by aqueous acid workup. This reduction is stronger than using NaBH₄.
Outline a multi-step synthetic route to convert ethanol to butanoic acid.
Step 1: Oxidation of ethanol to ethanal using acidified potassium dichromate(VI), distilled immediately. Step 2: Oxidation of ethanal to ethanoic acid, under reflux. Step 3: React ethanoic acid with PCl5 to make ethanoyl chloride. Step 4: React ethanoyl chloride with ethyl magnesium bromide. Step 5: Hydrolyse the product with dilute acid to form butan-2-ol. Step 6: Oxidise butan-2-ol using acidified potassium dichromate(VI), distilled immediately to form butanone. Step 7: Oxidise butanone to butanoic acid using acidified potassium dichromate(VI), under reflux.
What type of reaction is involved in converting an alcohol to an alkene using concentrated sulfuric acid?
This is an elimination reaction, specifically dehydration. The sulfuric acid acts as a dehydrating agent, removing water from the alcohol to form the alkene.
What reagents are required to convert a primary alcohol to an aldehyde?
Acidified Potassium Dichromate(VI) (K₂Cr₂O₇ / H⁺) with distillation to remove the aldehyde as it forms, preventing further oxidation to a carboxylic acid.
Identify the possible by-product(s) when reacting ethanol with excess concentrated sulfuric acid at 170°C.
The main organic by-product is diethyl ether, formed via intermolecular dehydration. Water is also produced. Polymerisation of ethene to form longer chain alkenes is another, minor possibility.
Describe the purpose of reflux in a chemical reaction.
Reflux allows a reaction to be heated at its boiling point for an extended period without loss of volatile reactants or products. This increases the reaction rate and yield.
Suggest a suitable reagent for converting a ketone to a secondary alcohol.
Sodium borohydride (NaBH₄) in ethanol is a suitable reducing agent. Alternatively, Lithium Aluminium Hydride (LiAlH₄) can be used, followed by dilute acid, but this is a stronger reducing agent and requires anhydrous conditions.
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