Q.(i) Write the R/S configurations of the following two chiral centres: (I) a carbon bearing OH (up), COOH (down), CH3 (right) and H (left) [i.e. lactic acid, CH3-CH(OH)-COOH, drawn in a cross projection]; and (II) a carbon bearing D (up, plain bond), NH2 (down, bold wedge) and H (right, bold wedge), with CH3 attached via a hashed/dashed bond [a deuterium-labelled 1-phenylethylamine-type stereocentre].

Both stereocentres are assigned by CIP priority rules with the 'reverse if lowest priority points toward viewer' correction; the chlorobenzene + chloral reaction is the classic DDT synthesis; and the iodoform test distinguishes the two ketones because only propanone has a methyl ketone group.

1. R/S configurations Centre I (lactic-acid type: OH up, COOH down, CH3 right, H left): CIP priority: $OH(1) > COOH(2) > CH_3(3) > H(4)$. This is a Fischer-type cross where horizontal bonds (here, H) point toward the viewer. Tracing $1\to2\to3$ (OH→COOH→CH3) as drawn gives an apparent counterclockwise path; since the lowest-priority group (H) points toward the viewer, the apparent sense must be reversed to get the true configuration — giving clockwise = R. Centre II (D up/plain, NH2 down/wedge, H right/wedge, CH3 left/dash): CIP priority: $NH_2(1) > CH_3(2) > D(3) > H(4)$ (a C substituent outranks D, and D outranks plain H by mass). Here the lowest priority (H) is on a bold wedge (toward viewer), so again the apparent rotation of $1\to2\to3$ (NH2→CH3→D) must be reversed. Tracing the given positions gives an apparent clockwise path, which reverses to counterclockwise = S. (Note: the printed figure mixes wedge and plain bonds in an unusual way for a single tetrahedral centre; the above follows the CIP method as faithfully as the described geometry allows.)
2. Chlorobenzene + Cl3C-CHO (chloral), conc. H2SO4: This is the industrial synthesis of the insecticide DDT: …