ChemistryChapter 19: Carbonyl Compounds
From Acid To Alcohol and Back
Reduction of carboxylic acids is harder than of aldehydes (LiAlH4 named if the book has it; NaBH4 often not enough).
Learning objectives
- Explain from acid to alcohol and back in simple chemical language.
- Connect 1. reduce with 2. oxidise up using equations, observations, or trends where needed.
- Answer a short Federal Board question with the correct terms and a clear reason.
Definition
Reduction of carboxylic acids is harder than of aldehydes (LiAlH4 named if the book has it; NaBH4 often not enough). Reverse: oxidise 1 alcohol all the way. Ester reduction named if asked. Meaning: oxidation state of carbon in COOH is high; you need a strong reductant name. Still exam names, not hydride-handling manuals. Acid + LiAlH4 or reduction gives primary alcohol; alcohol oxidised back to acid via aldehyde. Tollens distinguishes aldehyde from ketone; iodoform targets methyl carbonyl or ethanol specifically.
Important terms
- FROM ACID TO ALCOHOL AND BACK
- Reduction of carboxylic acids is harder than of aldehydes (LiAlH4 named if the book has it; NaBH4 often not enough).
- 1. REDUCE
- Acid -> 1 alcohol (named strong hydride).
- 2. OXIDISE UP
- 1 alcohol reflux dichromate -> acid.
Overview
Down the hill, then up:
Reduce
Acid -> 1 alcohol (named strong hydride). Aldehyde is the halfway if you could stop (hard). Nitrile + LiAlH4 -> amine named in the next chapter if linked. Ester link: acid + alcohol reversible; hydrolysis returns acid and alcohol.
Examples Ethanoic -> ethanol · LiAlH4 named · Not a SOP
Oxidise Up
1 alcohol reflux dichromate -> acid. Aldehyde also -> acid (Tollens conditions too). 2 alcohol stops at ketone. Interconversion map ties Ch18-21 synthesis.
Examples Ethanol -> ethanoic · Orange green · No 3 alcohol path
WHAT — FROM ACID TO ALCOHOL AND BACK
Reduction of carboxylic acids is harder than of aldehydes (LiAlH4 named if the book has it; NaBH4 often not enough). Reverse: oxidise 1 alcohol all the way. Ester reduction named if asked. Meaning: oxidation state of carbon in COOH is high; you need a strong reductant name. Still exam names, not hydride-handling manuals. Acid + LiAlH4 or reduction gives primary alcohol; alcohol oxidised back to acid via aldehyde. Tollens distinguishes aldehyde from ketone; iodoform targets methyl carbonyl or ethanol specifically.
WHY — Why this topic matters
FROM ACID TO ALCOHOL AND BACK is an independent FBISE learning unit because students must use its definitions, conditions, equations, or trends separately in explanations and calculations.
HOW — How it works
REDUCE: Acid -> 1 alcohol (named strong hydride). Aldehyde is the halfway if you could stop (hard). Nitrile + LiAlH4 -> amine named in the next chapter if linked. Ester link: acid + alcohol reversible; hydrolysis returns acid and alcohol. Examples: Ethanoic -> ethanol; LiAlH4 named; Not a SOP. OXIDISE UP: 1 alcohol reflux dichromate -> acid. Aldehyde also -> acid (Tollens conditions too). 2 alcohol stops at ketone. Interconversion map ties Ch18-21 synthesis. Examples: Ethanol -> ethanoic; Orange green; No 3 alcohol path. Exam hill: 1 alcohol -> aldehyde -> acid (ox) acid back to 1 alcohol needs a named strong reductant ketones do not become acids with Tollens
In simple words
Named redox. No hydride SOP, no illicit routes.
Key points
- LiAlH4 named for acids if in the book
- NaBH4 for aldehydes/ketones
- strong reductant name
- dichromate school
Exam preparation
Exam Focus
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.From Acid To Alcohol and Back
Sticky Notes · Quick Revision
Core Idea
- Reduction of carboxylic acids is harder than of aldehydes (LiAlH4 named if the book has it; NaBH4 often not enough). Reverse: oxidise 1 alcohol all the way. Ester reduction named if asked. Meaning: oxidation state of carbon in COOH is high; you need a strong reductant name. Still exam names, not hydride-handling manuals. Acid + LiAlH4 or reduction gives primary alcohol; alcohol oxidised back to acid via aldehyde. Tollens distinguishes aldehyde from ketone; iodoform targets methyl carbonyl or ethanol specifically.
1. REDUCE
- Acid -> 1 alcohol (named strong hydride). Aldehyde is the halfway if you could stop (hard). Nitrile + LiAlH4 -> amine named in the next chapter if linked. Ester link: acid + alcohol reversible; hydrolysis returns acid and alcohol.
- Ethanoic -> ethanol
- LiAlH4 named
- Not a SOP
2. OXIDISE UP
- 1 alcohol reflux dichromate -> acid. Aldehyde also -> acid (Tollens conditions too). 2 alcohol stops at ketone. Interconversion map ties Ch18-21 synthesis.
- Ethanol -> ethanoic
- Orange green
- No 3 alcohol path
Exam Example
- Exam hill:
- 1 alcohol -> aldehyde -> acid (ox)
- acid back to 1 alcohol needs a named strong reductant
- ketones do not become acids with Tollens
Common Misconceptions
- Do not confuse 1. REDUCE with 2. OXIDISE UP; state the difference before giving an example.
- Writing only “LiAlH4 named for acids if in the book” is not enough. Explain what it means in a complete sentence.
FBISE Exam Check
- Explain from acid to alcohol and back, compare its two main parts, and include the correct chemical evidence.
- Named redox. No hydride SOP, no illicit routes.
60-second revision
- Reduction of carboxylic acids is harder than of aldehydes (LiAlH4 named if the book has it; NaBH4 often not enough).
- 1. REDUCE: Acid -> 1 alcohol (named strong hydride).
- 2. OXIDISE UP: 1 alcohol reflux dichromate -> acid.
- Exam reminder: Exam hill: 1 alcohol -> aldehyde -> acid (ox) acid back to 1 alcohol needs a named strong reductant ketones do not become acids with Tollens
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