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From TBR Orgo Ch.2 phase 1 question 8:
How can a compound with an optical rotation of +233.0 be discerned from a compound with an optical rotation of -127.0?
A. The intensity of light is greater with the positive optical rotation
B. The sample with +233.0 optical rotation when diluted to half of its original concentration would show an optical rotation of +116.5
C. The larger the absolute value of the optical rotation, the greater the density of the compound
D. It is not possible to distinguish the two compounds from one another
I understand why A, C, and D are wrong leaving B the correct answer (good enough to get this question right)... but I don't quite understand how B answers the question stem.
I think my confusion has to due with my misunderstanding that optical rotations of +233.0 and -127.0 give the same reading.... From TBR's answer explanation, "When using a polarimeter, an observed optical rotation of +233.0 and -127.0 would result in the same reading (given that a full circle is 360). To discern one optical rotation from the other, the samples should be diluted to reduce the magnitude of the observed rotation."
Can y'all help me understand this?
How can a compound with an optical rotation of +233.0 be discerned from a compound with an optical rotation of -127.0?
A. The intensity of light is greater with the positive optical rotation
B. The sample with +233.0 optical rotation when diluted to half of its original concentration would show an optical rotation of +116.5
C. The larger the absolute value of the optical rotation, the greater the density of the compound
D. It is not possible to distinguish the two compounds from one another
I understand why A, C, and D are wrong leaving B the correct answer (good enough to get this question right)... but I don't quite understand how B answers the question stem.
I think my confusion has to due with my misunderstanding that optical rotations of +233.0 and -127.0 give the same reading.... From TBR's answer explanation, "When using a polarimeter, an observed optical rotation of +233.0 and -127.0 would result in the same reading (given that a full circle is 360). To discern one optical rotation from the other, the samples should be diluted to reduce the magnitude of the observed rotation."
Can y'all help me understand this?