This set of Organic Chemistry Multiple Choice Questions & Answers focuses on “Organometallic Compounds – 2”.
1. Which of the following statement is not true about ferrocene?
a) decamethyl ferrocene is staggered in solid state
b) cyclopentadienyl rings in ferrocene are almost eclipsed
c) cyclopentadienyl ring in ferrocene are staggered
d) ferrocene can be nitrated by reaction with dil. HNO3
Explanation: Cyclopentadienyl ring in ferrocene are staggered is a wrong statement. Cyclopentadienyl rings in ferrocene are eclipsed.
2. Ferrocene cannot undergo which of the following reaction?
a) Friedal craft acylation
b) Diels-Alder reaction
c) Oxidation by Ag + ions
d) Electrophilic substitution
Explanation: Ferrocene cannot undergo Diels-Alder reaction because it does not satisfy requirements of Diels-Alder reaction (dienophile).
3. Structurally nickelocene is similar to ferrocene but how Nickelocene attains stability?
a) due to formation of a monocation
b) due to formation of a dication
c) due to formation of a monoanion
d) due to formation of a dianion
Explanation: Nickelocene follows 20 e– rule. S, it attains stability by formation of dication.
4. Which of the following is/are true about ferrocene?
I. Ferrocene is diamagnetic
II. Dipole moment is zero
III. Kealy and Pauson synthesizes ferrocene from C5H5 and freshly reduced Fe
IV. Kealy and Pauson synthesises ferrocene from C5H5MgBr and FeCl3.
The correct answer is:
a) III and IV
b) I, II and III only
c) I, II and IV only
d) II, III and IV only
Explanation: Ferrocene is diamagnetic, Dipole moment is zero and Kealy and Pauson synthesizes ferrocene from C5H5 and freshly reduced at 300℃. But Kealy and Pauson does not synthesise ferrocene from C5H5MgBr and FeCl3.
5. Which type of boranes are B5H9 and B4H10 respectively?
a) Nido and Arachano boranes
b) Nido and closo boranes
c) Closo and Arachano boranes
d) Both are Nido
Explanation: As shown below B5H9 is Nido and B4H10 is Archano. SIngle-cluster boranes have the following general formulae, where “n” is the number of boron atoms: Nindo- BnHn+4 and Archano- BnHn+6.
B5H9 → (BH)5H4
x = 2, Nido
And, B4H10 → (BH)4H6
x = 3, Archano.
6. Mn(CO)5 is isolobal with which of the following compound?
Explanation: Two fragments are isolobal if the number, symmetry properties, approximate energy, and shape of the frontier orbitals and the number of electrons in them are similar.
[Mn(CO)5]: VEC = 7 + 5 × 2 = 17 → Stable No. 18
CH3: VEC = 4 + 3 = 7 → Stable No. 8
Both have deficiency of 1 e– from their stable no. Thus, [Mn(CO)5] & CH3 are isolobal.
7. Which of following pair is not isolobal?
a) Mn(CO)5, CH3
b) [Fe(CO)4], O
c) Mn(CO)5, Cl
d) Mn(CO)5, O
Explanation: [Mn(CO)5], CH3 are isolobal (Deficiency of 1 e–)
[Fe(CO)4]: VEC = 8 + 4 × 2 = 16 O → 6
Deficiency of 2e– from stable no., thus they are isolobal.
[Mn(CO)5, Cl] are isolobal (Deficiency of 1 e–).
[Mn(CO)5]: VEC = 17 (Deficiency of 1)
O: VEC = 6 (Deficiency of 2)
Thus, [Mn(CO)5], O are not isolobal.
8. According to wade’s Rule, [C2B10H12] adopts which type of structure?
a) closo structure
b) nido structure
c) archano structure
d) hypo structure
Explanation: C2B10H12 → (BH)10H2
(2(10)+2)/2 = 10+x
x = 1, Closo structure.
9. Which property is the same for isolobal molecules?
a) e– capture
b) Boiling point
c) Melting point
Explanation: Isolobal molecules have same deficiency of e– from their stable no. Thus, they have same e–.
10. Which of the following is not considered as an organometallic compound?
c) Ziese’s salt
d) Grignard reagent
Explanation: Cis-platin does not have metal-carbon bond. Therefore, cis platin not considered as organometallic chemistry.
Sanfoundry Global Education & Learning Series – Organic Chemistry.
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