SSC CGL Chemistry · Carbon and Its Compounds
Functional Groups and Reagents
Primary, secondary and tertiary alcohols, ethers, aldehyde and acid names, which acid is strongest, and the named reagents and catalysts: Grignard and Rosenmund.
Why this matters
Fifteen questions in the bank: nine from the 2023 shifts and six from the 2024 shifts, ten of them MODERATE. Many ask a name for a given formula, so learn how the names are built rather than each name alone.
Concept 1 of 2: Functional groups and their names
Definition
Alcohols: one carbon on the C-OH carbon gives a primary, two a secondary, three a tertiary alcohol. Butan-2-ol is secondary; tertiary butyl alcohol is 2-methylpropan-2-ol.
Other groups:
- Ether: an oxygen between two alkyl groups, R-O-R'.
- A -CHO on a ring takes the suffix carbaldehyde.
- (C6H5)2CO is benzophenone, a ketone.
- Acids by carbon count: methanoic (formic, HCOOH), ethanoic (acetic), propionic, butyric (four carbons).
- Formic acid is the strongest of these; each added alkyl group weakens the acid.
- Melting points: acetic acid 290 K (it freezes in cold weather), ethanol 156 K.
Practise this conceptself-check · 3 quick reps
The same idea in a real exam question:
Example 1 · Carbon and Its Compounds · Functional Groups and Reagents
Butan-2-ol is not a ketone
Concept 2 of 2: Named reagents and chemists
Definition
Reagents:
- Grignard reagent: R-Mg-X, an alkyl magnesium halide such as CH3-Mg-Cl. It forms when a haloalkane (or aryl or vinyl halide) reacts with magnesium in dry ether.
- Rosenmund catalyst: palladium on barium sulphate; it reduces an acyl chloride to an aldehyde.
- Tollens' and Fehling's reagents test for aldehydes; Hinsberg's reagent tells amines apart.
Chemists:
- H. C. Brown: diborane with aldehydes and ketones (organoboron chemistry).
- Vladimir Prelog: Nobel 1975, stereochemistry of organic molecules.
Practise this conceptself-check · 3 quick reps
The same idea in a real exam question:
Example 2 · Carbon and Its Compounds · Functional Groups and Reagents
Grignard needs magnesium
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Reference tables (2)
Watch out for (2)
- Butan-2-ol is not a ketone→ Functional groups and their names
- Grignard needs magnesium→ Named reagents and chemists
Test yourself on Carbon and Its Compounds
10 past SSC CGL questions from this chapter, timed at 6 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.