McMurry (Kap. 5,3)

Question 1

What is organic compounds called that are capable of rotating plane polarized light through an angle called (a)?

Answer 1

Optically active molecules.

Question 2

Is all molecules able to be optically active?

Answer 2

No, only chiral molecules.

Question 3

Some optically active molecules rotate the light (clockwise - to the right, and some (counterclockwise - to the left).

which is levorotatory and dextrorotatory?

Answer 3

(counterclockwise - to the left) - levorotatory.

(clockwise - to the right) - dextrorotatory

Question 4

Rotation of the light to the left or right is given a (-) and (+) sign.

Which is attributed to which?

Answer 4

(counterclockwise - to the left) - levorotatory ( - )

(clockwise - to the right) - dextrorotatory ( + )

Question 5

What standards can have an effect on the amount of rotation, and have to be standard (is standard when given the specific rotation of some molecules)

Answer 5

• The concentration of the molecule needs to be constant.
• the length of the sample tube needs to be constant.

The higher the concentration - the more the rotation.

The longer the length of the sample tube - the more the rotation

The wavelength of the light used is also important, and therefore the same light is used with the same wavelength every time

Question 6

how can the rotation of the light be calculated? is there a formula?

Answer 6

yes, see page 120.

Question 7

does two enantiomers rotate the light the same amount?

Answer 7

Yes, but one of the conformations rotate the light +x and the other -x.

x is the same number.