Question 1

What happens to the beta hydrogen during the conversion of two sigma bonds into a pi bond in an elimination reaction?

Accepted Answer

It is removed as a proton, allowing the formation of the pi bond.

Question 2

According to Zaitsev's Rule, which of the following is the major product in the E2 elimination of 2-bromo-3-methylpentane with NaOCH$$_3$$?

Accepted Answer

The alkene with the double bond between C2 and C3.

Question 3

Which of the following best explains why NaH leads to a faster E2 elimination than CH$$_3$$ONa, as shown in the reaction coordinate diagram?

Accepted Answer

Using stronger bases would result in a lower $$E_a.$$

Question 4

Which compound is the better SN2 substrate: 1-bromo-2-methylpropane or 3-bromopentane?

Accepted Answer

1-bromo-2-methylpropane

Question 5

In the reaction of 2-bromo-3,5,5-trimethylcyclohexane with CH$$_3O$^-$$, what is the major product?

Accepted Answer

A cyclohexane with a methoxy group at the equatorial position.

Question 6

Why does reaction (ii) in the provided scheme produce a thioether, while reaction (i) does not?

Accepted Answer

Reaction (ii) produces a thioether because ethanethiolate is more nucleophilic than ethanolate.

Question 7

Which of the following best describes the McLafferty rearrangement in 2-methyloctan-4-one?

Accepted Answer

A hydrogen atom is transferred from the gamma position to the carbonyl oxygen, resulting in a neutral alkene and an enol fragment.

Question 8

Determine the $$^1H $$NMR splitting pattern for the marked hydrogens in the given aromatic compound.

Accepted Answer

Hydrogen a: sharp singlet; Hydrogen b: singlet; Hydrogen c: triplet

Question 9

In the $$^1H $$NMR of 2-methyl-3-hexanone, the two methyl groups are equivalent and give one doublet. In the product after reaction with allyl magnesium bromide, the two methyl groups give different doublets. What is the term used to describe such groups?

Accepted Answer

Diastereotopic

Question 10

For 2-bromo-2-methylpropane, what is the expected $$^1H $$NMR spectrum?

Accepted Answer

A single sharp singlet integrating to 9H.

Question 11

How many $$^1H $$NMR signals are expected for (CH$$_3$$)$$_3$$CCH$$_2CH$_2CH$_2C(CH$_3$$)$$_3$$ and what are their multiplicities?

Accepted Answer

Four signals: singlet, triplet, triplet, singlet

Question 12

What are the expected chemical shifts (ppm) for the protons in the structure CH$$_3CH$_2Br$$?

Accepted Answer

Protons 'a' = $$\delta 3.5$$, protons 'b' = $$\delta 1.5$$

Question 13

Which of the following statements about the SN2 mechanism is correct?

Accepted Answer

The reaction proceeds with inversion of configuration at the electrophilic carbon.

Question 14

Which of the following best explains why tertiary alkyl halides do not undergo SN2 reactions efficiently?

Accepted Answer

Steric hindrance prevents backside attack by the nucleophile.

Question 15

In an E2 elimination, which of the following is required for the reaction to proceed efficiently?

Accepted Answer

The leaving group and the beta hydrogen must be anti-periplanar.

Organic Chemistry Exam 1 - Set 2 Study Guidance

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