MCQ : Important for NIPER JEE

Answers are declared !
1. Which of the following compounds would have the highest boiling point?
(a) CH3CH2CH2CH3
(b) CH3NH2
(c) CH3OH
(d) CH2F2
Answer:C
Explaination:This compound (methanol) forms the strongest hydrogen bonds of the available choices since oxygen is more electronegative than nitrogen. Although fluorine is more electronegative than oxygen there are no HF bonds in answer (d). Methanol also has some of the strongest dipole-dipole interactions of the available compounds although hydrogen bonding is the principle intermolecular attraction when a compound has an electropositive hydrogen atom and available non-bonding electron pairs.

2. The most stable conformational isomer of cis-1-bromo-2-chlorocyclohexane will have...
(a) both halide atoms in axial positions.
(b) both halide atoms in equatorial positions.
(c) the bromine atom in an axial position and the chlorine atom in an equatorial position.
(d) the bromine atom in an equatorial position and the chlorine atom in an axial position.
Answer:D
Explaination:The bromine atom is larger than the chlorine atom and should be placed in an equatorial position. The cis geometry requires that the chlorine atom be placed in an axial position.

3. How many dichlorinated isomers can be formed by the halogenation of CH3CH2CH2CH3 with Cl2 in the presence of light?
(a) 2
(b) 3
(c) 5
(d) 6
Answer:D
Explaination:The correct isomers are...1,1...1,2...1,3...1,4...2,2...2,3 dichlorobutanes

4. The CMR spectrum of an unknown compound shows 6 absorptions and the PMR spectrum shows 5 absorptions. Which of the following compounds is the unknown compound?

Answer:B

5.The most stable conformational isomer of trans-1-ethyl-2-methylcyclohexane will be...

Answer:C

6. The best nomenclature for the geometry of the following compound is...

(a) 1,3-pentamethylpropane
(b) 1,1,3,3-tetramethylbutane
(c) 2,4,4-trimethylpentane
(d) 2,2,4-trimethylpentane
Answer:C
Explaination:The priority of the 1-methylethyl group is higher than the 1-propyl group thus making the compound an E for "entgegen" (opposite in German).

7. Arrange the following groups in decreasing order of priority for E/Z nomenclature with the highest priority group listed first.

(a) B>A>C
(b) B>C>A
(c) A>C>B
(d) C>A>B
Answer:A
Explaination:The fluorine atom has the highest atomic mass and must be first followed by the isopropyl group, which by being branched has a higher priority than the pentyl group.

8.Which of the following is an intermediate in the reaction of benzene with CH3Cl and AlCl3?

Answer:C
Explaination:Aluminum chloride is a strong Lewis acid and reacts with methyl chloride to form a methyl carbocation, which is the electrophile in the next step of the reaction.

9. Which of the following represents the best resonance form for H2C=CHF?

Answer:C
Explaination:The fluorine atom must donate an electron pair to the double bond.

10.Which of the following compounds is the strongest Brønsted base?
(a) CH4
(b) NH3
(c) H2O
(d) HF
Answer:B
Explaination:Ammonia is the strongest base in this group. It has a non-bonded pair of electrons and has the lowest electronegativity in the group of compounds that has non-bonded electron pairs.

11. Which of the following compounds is the strongest Brønsted base?
(a) H2PO4-
(b) HSO4-
(c) NO3-
(d) CH3COO-
Answer: D
Explaination:All of the other bases have a full positive charge on the atom adjacent to the oxygen atom that has the negative charge. This will attract the electrons on the charged oxygen atom and make them less available for sharing. Another way to remember this is that the acetate ion will be the strongest base because acetic acid is the weakest acid in the group. A strong acid must logically create a weak conjugate base or the acid could not give up the proton readily.