O reativo de Tollens caracteriza os aldeídos pela reação:

$$\begin{array}{c}\mathrm{R}\end{array}-\begin{array}{c}\\ \\ \mathrm{C}\\ \Vert \\ \mathrm{O}\end{array}-\begin{array}{c}\mathrm{H}\end{array}+\mathrm{Ag}{}^{+}+\mathrm{H}{}_2\mathrm{O}\to \begin{array}{c}\mathrm{R}\end{array}-\begin{array}{c}\\ \\ \mathrm{C}\\ \Vert \\ \mathrm{O}\end{array}-\begin{array}{c}\mathrm{OH}\end{array}+\mathrm{Ag}+2\mathrm{H}{}^{+}$$

1) Indicar, com justificativa sumária, qual dos ácidos abaixo se comporta como aldeído frente ao reativo de Tollens:

$$\begin{array}{c}\mathrm{H}{}_3\mathrm{C}\end{array}-\begin{array}{c}\\ \\ \mathrm{C}\\ \Vert \\ \mathrm{O}\end{array}-\begin{array}{c}\mathrm{OH}\end{array}$$

$$\begin{array}{c}\mathrm{HO}\end{array}-\begin{array}{c}\\ \\ \mathrm{C}\\ \Vert \\ \mathrm{O}\end{array}-\begin{array}{c}\\ \\ \mathrm{C}\\ \Vert \\ \mathrm{O}\end{array}-\begin{array}{c}\mathrm{OH}\end{array}$$

$$\begin{array}{c}\mathrm{H}\end{array}-\begin{array}{c}\\ \\ \mathrm{C}\\ \Vert \\ \mathrm{O}\end{array}-\begin{array}{c}\mathrm{OH}\end{array}$$

$$\begin{array}{c}\mathrm{C}\ell \mathrm{CH}{}_2\end{array}-\begin{array}{c}\\ \\ \mathrm{C}\\ \Vert \\ \mathrm{O}\end{array}-\begin{array}{c}\mathrm{OH}\end{array}$$

2) Representar a reação estequiométrica para o caso desse ácido.