Question

Identify the three stereoisomers of the hydrobenzoin product using R and S descriptors. If there are three isomers, why are there only two product lines in the prelab table?

compound	mol. wt. (g/mol)	mmol	amount (g)       (mL)		m.p. (˚C)	density (g/mL)	ref.
benzil	210.23	2.38 mmol	.5g	-	94-95 °C (lit.)	1.23 g/mL
sodium borohydride	37.832 g/mol	2.64 mmol	.1g	-	400°C	1.375 g/mL
ethanol	46.07 g/mol	-	-	5 mL	-	0.789 g/mL
meso-hydrobenzoin	214.26 g/mol	2.38 mmol	.509g	-	137-139 °C (lit.)	1.193 g/mL
(±)-hydrobenzoin	214.264 g/mol	2.38 mmol	.509g	-	119-120 °C	1.0 g/mL

Answer 1

(+)hydrobenzoin and (-)hydrobenzoin are enantiomers. There all physical properties are same except their behavior with plane polarised light. There properties are same , that's why these two products are being added in same line.

Priority to the groups are based on atomic number, according to C.I.P. rule. Higher atomic number group gets higher priority. 4^th priority group should be placed into the plane of paper/board. Connect 1-2-3 , if direction is clockwise it is R otherwise it is S configuration of chiral Carbon.