Question 1

Which of the following molecular formulas has exactly 2 units of unsaturation? Use the formula $$[(2C+2)-(H-N+X)]/2$$ where $$C is $$the number of carbons, $$H is $$the number of hydrogens, $$N is $$the number of nitrogens, and $$X is $$the number of halides.

Accepted Answer

$$C_4H_6$$

Question 2

Which functional group is present in both adrenaline and dopamine, and is responsible for their classification as phenols?

Accepted Answer

A hydroxy group ($$-OH) $$attached to an aromatic ring

Question 3

Which of the following best describes the difference between a ketone and an aldehyde?

Accepted Answer

A ketone has two carbon groups attached to the carbonyl carbon, while an aldehyde has at least one hydrogen attached to the carbonyl carbon.

Question 4

Which of the following compounds contains a primary amine functional group?

Accepted Answer

$$CH_3CH_2NH_2$$

Question 5

Which of the following is NOT a valid resonance structure for the formamide anion ($$HCONH^-$$)?

Accepted Answer

A structure with 10 electrons around the central carbon atom

Question 6

Which of the following statements about resonance structures is TRUE?

Accepted Answer

Resonance structures differ only in the arrangement of electrons, not the arrangement of atoms.

Question 7

Which of the following functional groups contains a carbonyl group directly bonded to a halogen atom?

Accepted Answer

Acyl chloride

Question 8

A molecule with the formula $$C_3H_4$$ could have which of the following structures? (Select the one with the correct units of unsaturation.)

Accepted Answer

A three-membered ring with one double bond (cyclopropene)

Question 9

Which of the following best describes the resonance hybrid of a molecule?

Accepted Answer

A composite structure that shows the delocalization of electrons across all resonance forms

Question 10

Which of the following is a requirement for resonance to occur in a molecule?

Accepted Answer

The presence of lone pairs or $$\pi$$ electrons that can be delocalized

Question 11

Which of the following best describes a conjugated diene?

Accepted Answer

Two double bonds separated by one single bond

Question 12

Which of the following is the correct formula for calculating the units of unsaturation for a molecule containing carbon, hydrogen, nitrogen, and halogens?

Accepted Answer

$$[(2C+2)-(H-N+X)]/2$$

Question 13

Which of the following functional groups is present in methyl acetate?

Accepted Answer

Ester

Question 14

Which of the following statements about the movement of electrons in resonance structures is correct?

Accepted Answer

Only lone pairs and $$\pi-$$bond electrons can participate in resonance.

Question 15

Which of the following is a distinguishing feature of an aromatic compound?

Accepted Answer

A six-membered ring with three alternating double bonds

Question 16

Which of the following is a correct statement about the relationship between resonance structures and isomers?

Accepted Answer

Resonance structures differ only in electron arrangement, while isomers differ in both atom and electron arrangement.

Question 17

Which of the following best describes the effect of resonance on molecular stability?

Accepted Answer

Resonance delocalizes electrons, increasing the stability of the molecule.

Question 18

Which of the following is a valid resonance structure for the acetate ion ($$CH_3COO^-$$)?

Accepted Answer

A structure with the negative charge on either oxygen atom

Question 19

Which of the following is NOT a functional group containing a carbonyl ($$C=O) $$group?

Accepted Answer

Ether

Question 20

Which of the following best explains why the structure below is NOT a valid resonance structure for formamide anion ($$HCONH^-$$)?

$$\mathrm{H-C(=O)-N(H)_2}$$ with 10 electrons around carbon.

Accepted Answer

Carbon cannot have more than 8 electrons in its valence shell.

Molecular Representations, Functional Groups, and Resonance in Organic Chemistry

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