Question 1

Which of the following best explains why Grignard reagents must be prepared and used under anhydrous conditions?

Accepted Answer

Grignard reagents are strong bases and react rapidly with water to form alkanes, destroying the reagent.

Question 2

A chemist wants to synthesize 2-phenyl-2-propanol from benzene. Which sequence of reagents would accomplish this transformation?

Accepted Answer

1) $$\mathrm{Br_2$, $$FeBr_3$$}$$; 2) $$\mathrm{Mg, ether}$$; 3) $$\mathrm{(CH_3$)_2CO}$$; 4) $$\mathrm{H_3O^+}$$

Question 3

Which of the following statements about UV-vis spectroscopy of conjugated $$\pi$$ systems is correct?

Accepted Answer

Increasing the length of conjugation in a molecule causes the absorption maximum ($$\lambda_{max}) to $$shift to longer wavelengths (red shift).

Question 4

Which product is formed when benzene is treated with $$\mathrm{Br_2$} in $$the presence of $$\mathrm{$$FeBr_3$$}$$?

Accepted Answer

Bromobenzene

Question 5

A compound gives a strong absorption at $$\sim 1700\ \mathrm{cm}^{-1} in $$its IR spectrum and shows a singlet at $$\delta = 9.8$$ ppm in its $$^1H $$NMR spectrum. Which functional group is most likely present?

Accepted Answer

Aldehyde

Question 6

Which of the following is the correct order of reactivity toward nucleophilic acyl substitution for the following carboxylic acid derivatives?

Accepted Answer

$$\mathrm{Acid\ chloride} \u003e \mathrm{Anhydride} \u003e \mathrm{Ester} \u003e \mathrm{Amide}$$

Question 7

Which of the following best describes the mechanism of electrophilic aromatic substitution (EAS) when benzene reacts with $$\mathrm{$$HNO_3$$}$$ and $$\mathrm{H_2SO_4}$$?

Accepted Answer

Formation of a nitronium ion ($$\mathrm{NO_2$^+}$$), which acts as the electrophile and attacks the benzene ring.

Question 8

Which of the following statements about enolate chemistry is correct?

Accepted Answer

Enolates are ambident nucleophiles and can react at either the $$\alpha-$$carbon or the oxygen atom.

Question 9

A student attempts to synthesize an amide by reacting a carboxylic acid with an amine directly. The yield is very low. What is the best explanation?

Accepted Answer

The reaction is not efficient because the carboxylic acid and amine form a salt rather than undergoing condensation.

Question 10

Which of the following best explains why benzylic hydrogens are unusually reactive in free radical halogenation reactions?

Accepted Answer

The benzylic radical is stabilized by resonance with the aromatic ring.

Question 11

Which of the following statements about the acidity of phenol compared to cyclohexanol is correct?

Accepted Answer

Phenol is more acidic because its conjugate base is stabilized by resonance with the aromatic ring.

Question 12

Which of the following is a correct statement about the reactivity of aryl halides in nucleophilic aromatic substitution (NAS)?

Accepted Answer

Aryl halides are more reactive in NAS if they have strong electron-withdrawing groups ortho or para to the halide.

Question 13

Which of the following best describes the product of the reaction between an aldehyde and a primary amine under mildly acidic conditions?

Accepted Answer

An imine

Question 14

Which of the following statements about the structure of benzene is correct?

Accepted Answer

Benzene is planar and all C–C bonds are of equal length due to delocalized $$\pi$$ electrons.

Question 15

Which of the following best explains why amino acids are zwitterions at physiological pH?

Accepted Answer

The amino group is protonated ($$\mathrm{NH_3$^+}) $$and the carboxyl group is deprotonated ($$\mathrm{COO^-}) at pH 7.$$

Question 16

A chemist wants to convert a nitrile to a primary amine. Which reagent would be most appropriate?

Accepted Answer

$$\mathrm{$$LiAlH_4$$}$$ followed by water

Question 17

Which of the following is a correct statement about the reactivity of carboxylic acids in Fischer esterification?

Accepted Answer

The reaction is catalyzed by acid and is reversible; removal of water drives the reaction to completion.

Question 18

Which of the following best describes the role of transition metal catalysts in coupling reactions (e.g., Suzuki, Heck, or Stille reactions)?

Accepted Answer

They facilitate the formation of new C–C bonds by enabling oxidative addition and reductive elimination steps.

Question 19

Which of the following statements about aromatic heterocycles is correct?

Accepted Answer

Pyridine is less reactive than benzene toward electrophilic aromatic substitution due to the electron-withdrawing effect of nitrogen.

Organic Chemistry Course Syllabus and Topic Overview

Guida di studio - Domande di pratica

Study guide - Flashcard