Question

Problem 5.31 O The amino acid (S)-alanine has the physical characteristics listed under the structure. a. What is the melting point of (R)-alanine? b. How does the melting point of a racemic mixture of (R) and (S)-alanine compare OH to the melting point of (S)-alanine? NH c. What is the specific rotation of (R)-alanine, recorded under the same conditions (S)-alanine as the reported rotation of (S)-alanine? (a) 8.5 d. What is the optical rotation of a racemic mixture of (R)- and (S)-alanine? mp. 297" e. Label each of the following as optically active or inactive: a solution of pure (S)-alanine; an equal mixture of (R) and (S)-alanine; a solution that contains 75% (S) and 25% (R)-alanine,

Answer 1

etc. al Enantioners having same physical properties like Melting point boith boiling point density Thus (s)-alanine, (R) – alanine has same physical properties. i.e, both having sate Helting point. thus relting point of (R) -alanine is 2970c (c) Enantioners having suhe optical rotation Except sign. Jone The one Isoher rotates the oft plane of polarised light clock wife Direction, another Isoher rotate & plane of polarised light in Anti Cact Direction. Thus R-alanine, salanine has sane optical rotation but sign is opposite. specific rotation of (pja alanine is ~8.50

0 (zero Degree). (d) optical rotation of a Racenic mixture of (RJ-alanine and (s)-alanine is because Iso ter rotates clockwise Direction, another Isoher rotutes Anti-clock Direction, iNet rotation ė one

(e), a solution of pure (5) -alanine: optically active tan equal mixture of (R) and (5)-alanine: optically inactive a solution contains 75%(S) and 25 %. R-alanine optically active, Hudor so alanine