Learning Materials
Features
Discover
Chapter 28: Problem 77
Of the following, the one that is not a constituent of a nucleic acid chain is (a) purine base; (b) phosphate group; (c) glycerol; (d) pentose sugar; (e) pyrimidine base.
Over 30 million students worldwide already upgrade their learning with Vaia!
All the tools & learning materials you need for study success - in one app.
Get started for free
Which of the following fatty acids is unsaturated? (a) palmitic acid; (b) oleic acid; (c) lauric acid; (d) stearic acid; (e) none of these.
The coagulation of egg whites by boiling is an example of (a) saponification; (b) inversion of a sugar; (c) hydrolysis of a protein; (d) denaturation of a protein; (e) condensation of amino acids.
Write the formulas of the species expected if the amino acid phenylalanine is maintained in (a) \(1.0 \mathrm{M}\) HCl; (b) \(1.0 \mathrm{M} \mathrm{NaOH} ;\) (c) a buffer solution with \(\mathrm{pH}=5.7\).
If \(\mathrm{D}-(+)\) -glyceraldehyde is treated with \(\mathrm{HCN}\) in aqueous solution under basic conditions for three days at room temperature, cyanohydrins are formed (see Chapter 27). The cyanohydrins are not isolated, but are hydrolyzed to hydroxyacids in the same reaction mixture using dilute sulfuric acid. In this process, a new stereocenter is formed in the molecule. The products are diastereomers, formed in unequal amounts, and separable from each other by recrystallization because of their different physical properties, including solubilities. The trihydroxybutanoic acids are separated and then oxidized to tartaric acid with dilute nitric acid, which oxidizes only the primary alcohol group. (a) Ignoring stereochemistry, draw the reaction sequence for the transformations described above and hence deduce the structure of tartaric acid. (b) Starting from the Fischer projection of \(\mathrm{D}-(+)-\) glyceraldehyde and using the reaction scheme from part (a), draw Fischer projections of the two trihydroxybutanoic acids formed and designate the chiral centers as \(R\) or \(S\). (c) Starting from the Fischer projection of \(\mathrm{D}-(+)-\) glyceraldehyde and using the reaction scheme from part (a), draw Fischer projections of the two forms of tartaric acid formed and designate the chiral centers as \(R\) or \(S\). (d) One form of tartaric acid obtained is optically active, rotating the plane of polarized light in a negative sense \((-) .\) The other isomer formed, called meso-tartaric acid, is not optically active. Explain why the other isomer is not optically active. Draw the dashed-wedged line structure that corresponds to the Fischer projection of meso-tartaric acid. Can you describe how the two halves of the molecule are related? Using Fischer projections, write equations for the conversion of \(L-(-)-\) glyceraldehyde to tartaric acid. Show clearly the stereochemistry of the tartaric acids that are formed, and indicate whether you expect them to be optically active.
The term "epimer" is used to describe diastereomers that differ in the configuration about a single carbon atom. Which pairs of the eight possible aldopentoses are epimers?
What do you think about this solution?
We value your feedback to improve our textbook solutions.
Explanations 
Textbooks 
Exams 
GCSE 
IGCSE 
AS 
A Level 
International A Level 
University Admissions Tests 
Flashcards 
Vaia AI 
Notes 
Study Plans 
Study Sets 
Find a job 
Find a degree 
Student Deals 
Magazine 
Mobile App