31 Year NEET Questions: Some Basic Principles And Techniques- 3 - NEET MCQ

The possible isomers of the compound with molecular formula C₇H₈O is 5. These are

When many substituents are present, the numbering is done from the end where the sum of locants is the lowest (lowest sum rule)

2, 5, 6 trimethyl heptane (wrong) 2 + 5 + 6 = 13

2, 3, 6 TriMethyl Heptane (correct)

Huckel’s rule states that for aromaticity there must be (4n + 2)π electron present in compound where n is an integer

Due to presence two similar methyl group at same carbon atom, above compound doesn’t show geometrical isomerism.

Due to presence of four different groups on carbon,(C*) it is chiral

More is the electron - dificiency of the carbonyl carbon, greater will be the reactivity of the carbonyl compounds towards nucleophilic addition.

IR spectroscopy is used for the purification of cyclohexanone from a mixture of benzoic acid, isoamyl alcohol, cyclohexane and cyclohexanone. Because in this method, each functional group uppear at a certain peak.
So, cyclohexanone can be identified by carbonyl peak.

Tautomerism is exhibited by  the oscillation of hydrogen atom between two polyvalent atoms present in the molecule. As option (d) has α-hydrogen atom.  Therefore it shows tautomerism whereas other structures do not.

When (–) 2 bromo octane is allowed to react with sodium hydroxide under given conditions, where second order kinetics are followed, the product obtained is (+) 2 octanol.

In this reaction Walden Inversion takes place so it is an example of S_N 2-reaction.

In arenes, π electrons are delocalised, hence arenes do not undergo addition reactions easily. Aromatic compounds (Arenes) are highly stable and show resorance. eg. Benzene is the simplest example.

Order of stability : staggered anti > gauche > skew boat > eclipsed.
Newmann projection of n butane is given as

The maximum staggered conformation is most stable in which methyl groups are far apart as for as possible, due to minimum repulsion between methyl groups and is also called anti conformation.

–OCH₃ activates the benzene ring. –NO₂ deactivates the ring. Hence the reaction of the given compounds with electrophiles is in the order, I > II > III

As in this compound the common groups i.e highly electronegative halogen atoms are on opposite side, hence it is a trans isomer.
Thus its name is trans-2-chloro-3-iodo-2-pentene.

—Cl atom sh ows o/p-dir ective influence but deactivate the benzene ring, while [—OH/—CH₃] groups show o/p  influence but activate the benzene ring but in these —OH group is more activating than —CH₃.
Hence order of electrophilic substitution

Due to absence of a symmetric (chiral) C-atom. D — CH₂ — CH₂ — CH₂Cl molecule is not a chiral molecule.

The compound is diethyl ether (CH₃CH₂)₂O which is resistant to nucleophilic attack by hydroxyl ion due to absent of double or triple bond, whereas all other compounds given are unsaturated

The atom or group which has more power to attract electrons in comparision to hydrogen is said to have -I effect. Thus higher the electronegativity of atom stronger will be the -I effect. As electronegativity of N, O & F follow the order N < O < F hence  based upon electronegative character order of-I effect is – NR₂ < – OR < – F.

When similar atoms are on opposite side the compound is in trans-form

Chiral molecules are those molecules which have atleast one symmetric carbon atom (a carbon atom attached to 4 different groups).
This is true in case of 3-methyl pentanoic acid.

Electron with drawing group (–NO₂) increases acidity while electron releasing group (–CH₃, –H) decreases acidity. Also effect will be more if functional group present at para position then ortho and meta position.

Stability of an alkene depends upon the heat of hydrogenation of an alkene. The lower the heat of hydrogenation of an alkene higher will be stability.

CH₃ and NH₂ are electron repelling groups, whereas NO₂ and OH are electron attracting groups and they leave the benzene ring deactivated. Due to stronger electron attracting (–I effect) effect of NO₂ group C₆H₅NO₂ shows least reactivity towards electrophilic substitution.

A compound is said to exhibi top tical isomerism if it atleast contains one chiral carbon atom, which is an atom bonded to 4 different atoms or groups

Electron releasing group (–CH₃)decreases acidity while electron withdrawing group (– NO₂)increases acidity.

The principle of steam distillation is based on Dalton's law of partial pressures. Suppose p₁ and p₂ be the vapour pressures of water vapour and the toluene at the distillation temperature. Toluene boils  when total pressure is equal to atmospheric pressure p i.e p  = p₁ + p₂ or  p₂ = p – p₁ as a result when toluene boil in  the presence of steam. Its partial pressure p₂ is less than atmospheric pressure.

The IUPAC name of

is Hex-1-en-5-yne or 1-hexene-5-yne The lowest number is given to the C = C double bond.

both are resonating structures.

Geometrical isomers differ in spatial arrangement of atoms.