The reactions of amino acids

This is the standard test for amino acids. The suspect amino acid solution is placed on a piece of filter paper and allowed to dry. This paper is then sprayed with ninhydrin solution, dried again, and placed in an oven at 110�C for 10 minutes. Red, blue and purple spots develop if amino acids are present. Do not worry about the exact structure of ninhydrin or the reaction involved. We shall be using this test in the chromatography experiment that follows. Consequently no video is shown at this stage as you will see it in the next experiment. Ninhydrin is used in forensic work to develop poor fingerprints.

ninhydrin

Molecules which have a chiral centre are optically active. In this experiment we use a polarimeter to measure the optical rotation of a number of amino acid solutions. Check the above theory link and look at the structures of the molecules tested at the bottom of the page. Make a note of the rotations and try to explain the observations from the video. Check your answer using the link below. Sodium glutamate, a salt of the amino acid, glutamic acid is a well-known optically active compound. It is better known as monosodium glutamate, the flavour enhancer popular in Chinese cookery.

glycine

alanine

phenylalanine