[curiouscat]

Wikipedia reports that the optical rotation of D-Catechin [α]_D = +14.0°

Merck Index reports 16° to 18° (at 18°C) Close enough.

Neither mentions a solvent. Does solvent matter a lot for quantitation of optical purity?

Is there a convention as to what solvent to use when not mentioned? How about the concentration?

Anyone else have a source for this optical rotation of D-Catechin?

I found one article, http://www.mdpi.com/1420-3049/15/8/5595/pdf but the value it reports for optical rotation (see Table 1 ) is 56° .  Totally at odds with both Wikipedia & the Merck Index. 

The article says  (c 1, acetone). I suppose that meant they used acetone as a solvent & a concentration of 1 gm/ml? Sounds a very high conc. Am I misreading this? 

[mjc123]

Aldrich gives for the hydrate (.xH₂O) 26° (c1, H₂O). So I guess the solvent does matter.
I think the concentration is conventionally in g/100 mL. See http://en.wikipedia.org/wiki/Specific_rotation.

[MOTOBALL]

CRC Handbook of Chemistry & Physics (1978) gives specific rotation as +18.4 deg at 18 deg. C.
No solvent given.

[curiouscat]

Thanks for those values!