Organic Synthesis and Analysis
31.1 Synthetic Routes:
Reducing agents: 31.1 Synthetic Routes
- NaBH4 will reduce C=O but not C=C. It can be used in aqueous solution. This is 31.2 organic analysis
because it produces the nucleophile :H- which attacks C𝛿+ but is repelled by the
electron rich C=C.
- Hydrogen with a nickel catalyst (H2/Ni)
is used to reduce C=C
- Tin and hydrochloric acid (Sn/H+) is used
to reduce R-NO2 to R-NH2.
Oxidising agents
- K2Cr2O7 acidified with sulfuric acid will
oxidise primary alcohols to aldehydes,
secondary alcohols to ketones, and
aldehydes to carboxylic acids.
Dehydrating agents:
- Heated aluminium oxide
- Acid-catalysed elimination using H3PO4
31.2 Organic Analysis:
Chemical reactions:
Functional Group Test Result
Alkene Shake with bromine water Red-brown colour disappears, turns to
colourless
Halogenoalkane Add NaOH(aq) and warm, acidify with Precipitate of AgX
HNO3 add AgNO3(aq)
Alcohol Add acidified K2Cr2O7 Orange colour turns green with primary,
secondary alcohols or aldehydes
Aldehyde Warm with Tollens solution Silver mirror forms
Warm with Fehling’s solution Blue colour turns to red precipitate
Carboxylic acid Add NaHCO3 Bubbles observed as carbon dioxide given off.
- When designing a synthetic pathway, we must consider many things:
o Cost
o Product yield
o Reaction conditions
o Process involved
o Formation of isomers
31.1 Synthetic Routes:
Reducing agents: 31.1 Synthetic Routes
- NaBH4 will reduce C=O but not C=C. It can be used in aqueous solution. This is 31.2 organic analysis
because it produces the nucleophile :H- which attacks C𝛿+ but is repelled by the
electron rich C=C.
- Hydrogen with a nickel catalyst (H2/Ni)
is used to reduce C=C
- Tin and hydrochloric acid (Sn/H+) is used
to reduce R-NO2 to R-NH2.
Oxidising agents
- K2Cr2O7 acidified with sulfuric acid will
oxidise primary alcohols to aldehydes,
secondary alcohols to ketones, and
aldehydes to carboxylic acids.
Dehydrating agents:
- Heated aluminium oxide
- Acid-catalysed elimination using H3PO4
31.2 Organic Analysis:
Chemical reactions:
Functional Group Test Result
Alkene Shake with bromine water Red-brown colour disappears, turns to
colourless
Halogenoalkane Add NaOH(aq) and warm, acidify with Precipitate of AgX
HNO3 add AgNO3(aq)
Alcohol Add acidified K2Cr2O7 Orange colour turns green with primary,
secondary alcohols or aldehydes
Aldehyde Warm with Tollens solution Silver mirror forms
Warm with Fehling’s solution Blue colour turns to red precipitate
Carboxylic acid Add NaHCO3 Bubbles observed as carbon dioxide given off.
- When designing a synthetic pathway, we must consider many things:
o Cost
o Product yield
o Reaction conditions
o Process involved
o Formation of isomers
