Tell whether each of the following reactions is likely to be SN 1, SN 2, E 1, E 1 cB or E2: (a)

step 1 Hey guys, in this problem we will determine the type of the following reactions whether they are

Tell whether each of the following reactions is likely to be...

Tell whether each of the following reactions is likely to be $\mathrm{S}_{\mathrm{N}} 1, \mathrm{~S}_{\mathrm{N}} 2, \mathrm{E} 1, \mathrm{E} 1 \mathrm{cB}$ or E2: (a) $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{Br} \quad \frac{\mathrm{NaN}_{3}}{\mathrm{THF}} \quad \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{~N}=\mathrm{N}=\mathrm{N}$ (b) (c) (d)

Tell whether each of the following reactions is likely to be $\mathrm{S}_{\mathrm{N}} 1, \mathrm{~S}_{\mathrm{N}} 2, \mathrm{E} 1, \mathrm{E} 1 \mathrm{cB}$ or E2:
(a) $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{Br} \quad \frac{\mathrm{NaN}_{3}}{\mathrm{THF}} \quad \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{~N}=\mathrm{N}=\mathrm{N}$
(b)
(c)
(d)

Key Concepts

SN1 Reaction Mechanism

The SN1 reaction mechanism is characterized by a two-step process where the leaving group first dissociates, forming a carbocation intermediate. The rate-determining step is the formation of this carbocation, and the overall reaction rate depends solely on the substrate. This mechanism is favored by substrates that can stabilize carbocations, typically tertiary or resonance-stabilized systems, as well as by polar protic solvents that help stabilize charged intermediates.

SN2 Reaction Mechanism

The SN2 reaction mechanism involves a single concerted step where the nucleophile attacks the substrate from the opposite side of the leaving group, leading to a simultaneous bond-forming and bond-breaking process. The reaction rate depends on both the substrate and the nucleophile concentrations. This mechanism is typically favored by primary substrates with less steric hindrance, strong nucleophiles, and polar aprotic solvents that do not strongly interact with the nucleophile.

E1 Reaction Mechanism

The E1 reaction mechanism proceeds through a two-step process similar to SN1, starting with the formation of a carbocation intermediate after the leaving group exits. Subsequently, a base abstracts a proton from a neighboring carbon, resulting in the formation of a double bond. This pathway is favored under conditions that promote carbocation formation, such as the use of weak bases and polar protic solvents, and when the substrate can generate a stable carbocation.

E1cB Reaction Mechanism

The E1cB reaction mechanism involves an initial deprotonation step where a base removes a proton to form a carbanion intermediate that is often stabilized by adjacent electron-withdrawing groups. In the following step, the leaving group departs, leading to the formation of a double bond. This mechanism is typically seen when the leaving group is poor or when the formation of a stabilized anion is more favorable than the formation of a carbocation.

E2 Reaction Mechanism

The E2 reaction mechanism is a single-step, concerted process where a strong base simultaneously abstracts a proton and causes the leaving group to depart, forming a double bond in one go. The reaction rate depends on both the substrate and the base. E2 reactions are generally favored by strong bases, good leaving groups, and substrates in which the formation of a double bond is geometrically feasible, often requiring an anti-periplanar arrangement between the abstracted hydrogen and the leaving group.

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