NEET Chemistry Questions: Basic Principles of Orgainc Chemistry

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Arrange the following nucleophiles in the order of their nucleophilic strength –




No explanation available.
The nucleophilicities of CH3–, NH2–, OH– and F– decrease in the order -




The nucleophilicity order $CH_3– > NH_2– > OH– > F–$ is determined by the basicity and the polarizability of the nucleophiles. Methyl anion ($CH_3–$) is the strongest nucleophile due to its high electron density and low electronegativity of carbon. Amide ion ($NH_2–$) comes next, followed by hydroxide ion ($OH–$), and finally fluoride ion ($F–$) is the weakest nucleophile because of its high electronegativity and low polarizability.
Heterolysis of carbon-chlorine bond produces




Heterolysis refers to the cleavage of a bond in a molecule where both electrons of the bond are taken by one of the atoms, resulting in the formation of a cation (positively charged ion) and an anion (negatively charged ion). In the case of the carbon-chlorine bond, heterolysis produces a carbon cation (carbocation) and a chlorine anion (Cl-).
The reaction $(CH_3)_3 C— Br -> (CH_3)C+ + Br–$ is an example of




The reaction $(CH_3)_3C—Br -> (CH_3)_3C^+ + Br^-$ is an example of heterolytic fission. In heterolytic fission, the bond breaks unevenly, with one atom retaining both of the bonding electrons, resulting in the formation of a cation (positively charged ion) and an anion (negatively charged ion). Here, the bond between carbon and bromine breaks heterolytically to produce a carbocation $(CH_3)_3C^+$ and a bromide anion $Br^-$.
Which species represents the electrophile in aromatic nitration?




In aromatic nitration, the electrophile is $NO_2^+$. Electrophiles are species that accept an electron pair during a reaction. The nitration of benzene involves the generation of the nitronium ion ($NO_2^+$) as the electrophile, which then attacks the electron-rich aromatic ring to form the nitrobenzene compound.
The most stable carbonium ion among the following is




No explanation available.
Which of the following is the least stable carbanion?




The least stable carbanion among the given options is $ (CH_3)_3 C^- $. This is because the carbanion is highly destabilized by the inductive effect of the three methyl groups which donate electron density to the negatively charged carbon, increasing electron-electron repulsion and thus making it less stable.
Which of the following is the most stable free radical?




The most stable free radical among the given options is $C_6 H_5 CHCH_3 $. This is an allylic radical stabilized by resonance with the benzene ring. The unpaired electron can be delocalized over the aromatic ring, providing extra stability compared to the other given free radicals.
Which of the following is the most stable carbocation (carbonium ion)?




The stability of carbocations depends on the number of alkyl groups attached to the positively charged carbon. More alkyl groups increase the stability due to the electron-donating inductive effect and hyperconjugation. In this case, $(CH_3)_3C^+$ (tertiary carbocation) is the most stable because it has three alkyl groups stabilizing the positive charge.
What is the decreasing order of stability of the following ions? $(i) CH_3—C+H—CH_3 (ii) CH_3—C+H—OCH_3 and (ii) CH_3—C+H—COCH_3$




No explanation available.
Decreasing – I power of given groups is -(a) CN (b) $NO_2$ (c) $– NH_2$ (d) F




The –I (inductive) effect is the electron-withdrawing effect of a substituent. The order of decreasing –I power for the given groups is $NO_2 > CN > F > –NH_2$. The $NO_2$ group has the strongest electron-withdrawing effect, followed by $CN$, then $F$, and lastly $–NH_2$.
The reaction $C_2H_5Br + KOH ? C_2H_5OH + KBr$ is an example of




The reaction $C_2H_5Br + KOH \rightarrow C_2H_5OH + KBr$ involves the substitution of the bromine atom in ethyl bromide ($C_2H_5Br$) with a hydroxyl group ($OH^-$) from potassium hydroxide (KOH). This is a classic example of a nucleophilic substitution reaction where the nucleophile $OH^-$ attacks the electrophilic carbon atom bonded to the bromine.
Which of the following reactions is an example of elimination reaction?




The dehydration of ethanol ($C_2H_5OH \rightarrow C_2H_4 + H_2O$) is an example of an elimination reaction. In this reaction, a molecule of water is eliminated from ethanol to form ethene ($C_2H_4$). This type of reaction is characterized by the removal of a small molecule (in this case, water) from a larger molecule.
Propyne and propene can be distinguished by




Propyne ($C_3H_4$) and propene ($C_3H_6$) can be distinguished using $AgNO_3$ in ammonia. Propyne, being a terminal alkyne, reacts with $AgNO_3$ in ammonia to form a precipitate of silver acetylide, whereas propene, being an alkene, does not react with $AgNO_3$ in ammonia. This difference in reactivity is used to distinguish between the two compounds.
Which of the following has the smallest heat of hydrogenation per mole?




Trans-2-butene has the smallest heat of hydrogenation per mole among the given options. This is because trans isomers are generally more stable than their cis counterparts due to less steric hindrance between the bulky groups on the double bond. The stability of a compound is inversely related to its heat of hydrogenation. Therefore, trans-2-butene, being the most stable, has the smallest heat of hydrogenation.