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

Key Idea: The carbon which is more electrophilic in nature, loses an $\mathrm{\alpha }$-H with a base more readily. Among the given compounds, carbonyl carbon (>C=O) ie, ketone is more electrophilic in nature, thus loses an $\mathrm{\alpha }$

(d) The acidity of halogenated acid increases almost proportionately with the increase in electronegativity of the halogen present.

So, the correct order is:

FCH₂COOH > CICH₂COOH > BrCH₂COOH > CH₃ COOH

(d) An optically active compound rotate plane polarized light. But due to some external compensation (heat, light, catalyst, solvent etc), the optically active compound lose their optical activity. The compound then exists as racemic mixture i.e, both d and l form are present in solution due to some intramolecular rearrangement.

So, there is no rotation of plane polarised light and compound does not have an asymmetric centre and when it again forms the symmetric centre both d- and l forms are obtained in equal amount.

Halogens are the most reactive elements. High reactivity is due to their low dissociation energy. Further among halogens reactivity decreases as we move down the group. 

In case of different nucleophiles, but present in the same group in the periodic table, then larger is the atomic mass, higher is the nucleophilicity. Hence the decreasing order of nucleophilicity of the halide ions is I- > Br- > Cl- > F- 

Carbanions are nucleophilic species that can initiate both addition and substitution reactions. They can attack electrophilic centers in molecules, leading to addition reactions, or displace leaving groups, resulting in substitution reactions.

(d) These are characteristics of carbanion

According to the context provided under 'Many misconceptions are associated with resonance and the same need to be dispelled. You should remember that:', 'The molecule does not exist for a certain fraction of time in one canonical form and for other fractions of time in other canonical forms.' Instead, the resonance hybrid is a single, real structure that is an average of all contributing canonical forms.

The context states: 'Among the resonance structures, the one which has more number of covalent bonds, all the atoms with octet of electrons (except hydrogen which has a duplet), less separation of opposite charges, (a negative charge if any on more electronegative atom, a positive charge if any on more electropositive atom) and more dispersal of charge, is more stable than others.'

The context mentions: 'The concept of resonance was introduced to deal with the type of difficulty experienced in the depiction of accurate structures of molecules like O3. According to the concept of resonance, whenever a single Lewis structure cannot describe a molecule accurately, a number of structures with similar energy, positions of nuclei, bonding and non-bonding pairs of electrons are taken as the canonical structures...'

For $\text{CH}_3\text{COO}^{-}$, the two resonance structures involve the negative charge being delocalized between the two oxygen atoms, with the carbon atom having a complete octet in both. These structures are equivalent in energy and thus equally stable, making them significant contributors to the resonance hybrid.