Lactic Acid: A Case Study in Chirality

The video tutorial explains the concept of chiral carbons in lactic acid, focusing on the central carbon atom attached to four different groups. It describes the three isomeric forms of lactic acid: D lactic acid, which is dextro rotatory and found in meat extract; L lactic acid, which is levorotatory and present in fermented sucrose; and the racemic mixture, which shows no rotation due to external compensation. The video also covers the specific rotations of these isomers and their representation using Fischer projection formulas.

What makes the central carbon atom in lactic acid a chiral center?

• It is attached to four identical groups.

• It is attached to two identical and two different groups.

• It is attached to three different groups.

• It is attached to four different groups.

Which direction does D-lactic acid rotate plane-polarized light?

• Downwards

• To the left

• To the right

• Upwards

Where is D-lactic acid naturally found?

• In fresh fruits

• In fermented sucrose

• In meat extract

• In SO milk

What is the specific rotation of L-lactic acid?

• +5.0°

• -2.5°

• +2.5°

• 0°

What is the result when D and L lactic acids are mixed in equal amounts?

• The mixture shows no net rotation

• The mixture rotates light to the right

• The mixture rotates light upwards

• The mixture rotates light to the left