The correct corresponding order of names of the four aldoses with the configurations (1)–(4) shown below, respectively, is:

Solution & Explanation

\textbf{Answer:} (D) The four projections are D-erythrose, D-threose, L-erythrose, L-threose. \textbf{Solution:} For an aldotetrose the configuration of the lowest chiral carbon (C-3, adjacent to $\mathrm{CH}{}_2\mathrm{OH}$) fixes the D/L label: $-\mathrm{OH}$ on the right $=$ D, $-\mathrm{OH}$ on the left $=$ L. Erythrose (erythro) has the two $-\mathrm{OH}$ groups on the same side; threose (threo) has them on opposite sides. Structure (1): both $-\mathrm{OH}$ on right $\Rightarrow$ D-erythrose. Structure (2): C-2 $-\mathrm{OH}$ left, C-3 $-\mathrm{OH}$ right $\Rightarrow$ D-threose. Structure (3): both $-\mathrm{OH}$ on left $\Rightarrow$ L-erythrose. Structure (4): C-2 $-\mathrm{OH}$ right, C-3 $-\mathrm{OH}$ left $\Rightarrow$ L-threose. This matches option D.