Basic Principles of Orgainc Chemistry MCQs for NEET — Chemistry Questions with Answers

(d) Isomers which are possible by rotation about single bonds without cleavage of any bond are called conformers. In ethane, an infinite number of conformations are possible. There are two extreme forms, the staggered conformation, which is the most stable and the eclipsed conformation which is least stable. Among the conformers of ethane, bond angle and bond length remain same while their energy, stability and dihedral angle are different.

(b) Greater the s-character of C-atom in hydrocarbons, greater the electronegativity of

that carbon and thus greater the acidic nature of the H attached to electronegative carbon.

                        CH≡CH CH₂=CH₂ CH₃-CH₃

Hybridisation:         sp        sp2        sp3

s-character:          50%      33%       25%

Electronegativity:     â†Max.---------------------------------------

Acidic character      â†Max.---------------------------------------

of terminal H

Thus, CH≡CH > CH₃C≡CH > CH₂=CH₂ > CH₃-CH₃

The staggered conformation of ethane is more stable than the eclipsed conformation because it has no torsional strain. In the staggered conformation, the hydrogen atoms are arranged in a way that minimizes the steric repulsion between them, resulting in lower potential energy.

Toluene is the most reactive towards electrophilic nitration among the given options. The methyl group being an electron-donating substituent activates the benzene ring, making it more susceptible to electrophilic attack by the nitro group.

The correct order of decreasing acid strength is: trifluoroacetic acid (B) > trichloroacetic acid (A) > formic acid (D) > acetic acid (C). The highly electronegative fluorine and chlorine atoms withdraw electrons, making the respective acids stronger than acetic and formic acids.

(d) Key Idea Lesser the electron density of acyl carbon atom, more will be the susceptibility of nucleophile to attack it.

The Cl atom has strong -I effect and weakest +R effect because of the weak p-bond between the small sized C-atom and large sized Cl atom.

Thus, in CH₃COCl, acyl carbon has least electron density and hence, more susceptible for nucleophilic attack.

(d) Double bond have preference over triple bond while naming CH$\equiv$C-CH=CH₂
                                                                                       1-butene 3-yne