Which of the following best represents the transition state for an $S{N}_2$ reaction involving $C_2{H}_5\mathrm{Br}$ and $\mathrm{OH}-$ as the nucleophile?

Which of the following molecules is most likely to undergo an $E1$ mechanism when stirred in methanol?

What is the product of the nucleophilic substitution reaction when ${\mathrm{CH}}_3\mathrm{Br}$ reacts with $\mathrm{OH}-$ in aqueous solution?

For a certain nucleophilic substitution reaction, the rate of substitution is found to depend only on the concentration of the substrate and not on the concentration of the nucleophile. Which type of mechanism is most likely operating in this reaction?

Which of the following is the major product formed when 2-bromobutane undergoes a bimolecular elimination ($E_2$) reaction with a strong base?

Which of the following is the major organic product formed in an $S_1$ (SN1) reaction of $t_3\mathrm{-butyl}\mathrm{bromide}$ with water as the nucleophile?

Which of the following best describes the outcome when the ${\mathrm{acetylide}}_{-}$ ion reacts with $\mathrm{CH}{3}_{}\mathrm{OH}$ in a nucleophilic substitution reaction?

Which of the following compounds can be prepared by reacting an alkyl iodide with a suitable nucleophile in a nucleophilic substitution reaction?