SSC CGL 2024 Tier-I · 13 September 2024, Shift 3 · General Awareness · Question 23 of 100

Text as printed on a candidate's response sheet for this shift; answer per SSC's tentative key as marked on that sheet. Solution last reviewed 10 September 2026.

Where this paper and its answers come from

SSC does not publish CGL question papers or a public answer key. The questions and options here are reproduced as printed on a candidate's own response sheet for this shift — the Commission's text, unchanged. Each answer is SSC's tentative key as marked on that sheet; SSC allowed challenges to it and never publishes a final key. The solutions are written by UnlockIAS.

Grignard reagent is represented as:

(a)H-Mg-H
(b)CH₃-Ca-F
(c)CH₃-Be-F
(d)CH₃-Mg-Cl

Answer

Why

Correct — D. A Grignard reagent is an alkyl or aryl magnesium halide, general formula RMgX.

In option (d), CH₃-Mg-Cl, R is the methyl group, the metal is magnesium and X is chlorine. That is methylmagnesium chloride.

Test every option for all three parts — an organic group, magnesium, a halogen. Only option (d) has them all.

Why the others are wrong

(a)
H-Mg-H — H-Mg-H is magnesium hydride, MgH₂. It has magnesium but no carbon group and no halogen, so there is no carbon-metal bond at all.
(b)
CH₃-Ca-F — CH₃-Ca-F has calcium where the reagent needs magnesium. Its halogen is also the one NCERT leaves out: the textbook forms these compounds from chlorides, bromides and iodides.
(c)
CH₃-Be-F — CH₃-Be-F swaps in beryllium, magnesium's neighbour in Group 2. Same group, different element — the reagent Grignard discovered is built on magnesium.

Concept

Grignard reagents are organometallic compounds — they contain a carbon-metal bond. NCERT Class 12 describes them as alkyl magnesium halides, RMgX, discovered by Victor Grignard in 1900.

They are made by treating a haloalkane with magnesium metal in dry ether:
CH₃Cl + Mg → CH₃MgCl

They react with any source of a proton, even water, to give a hydrocarbon. That is why they must be prepared free of moisture.

The hyphens in the options are a convenience. NCERT notes that the carbon-magnesium bond is covalent but highly polar, while the magnesium-halogen bond is essentially ionic.

Key facts

A Grignard reagent is an alkyl or aryl magnesium halide with the general formula RMgX.
It is prepared by reacting a haloalkane with magnesium metal in dry ether.
Victor Grignard first reported these reagents in 1900 and shared the 1912 Nobel Prize in Chemistry with Paul Sabatier.
Grignard reagents react with water to give hydrocarbons, so they are prepared under anhydrous conditions.

Study next

Organometallic compounds and the carbon-metal bondReactions of haloalkanes with metals — the Grignard reagent and the Wurtz reactionNamed reagents in organic chemistry: Tollens', Fehling's, Hinsberg and Grignard

Common traps

Accepting another Group 2 metal in place of magnesium because the rest of the formula looks right.
Forgetting the organic group — H-Mg-H contains magnesium but is a plain hydride.

The same reagent is asked from the other direction at 11 Sep 2024, 12:30, GA Q.8, which names the reactants — halides and magnesium metal — and asks for the reagent they yield.

Related PYQs

No directly related past PYQ was found.

Topic: Scientific Research — all 152 SSC CGL questions on it, every solved shift.