Chapter 21: Q121E (page 888)
Which base will hydrogen-bond with uracil within an RNA molecule? Draw the structure of this base pair.
Uracil forms a base pair with adenine.
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Give the structure for each of the following aromatic hydrocarbons.
a. o-ethyltoluene
b. p-di-tert-butylbenzene
c. m-diethylbenzene
d. 1-phenyl-2-butene.
Question: Polycarbonates are a class of thermoplastic polymers that are used in the plastic lenses of eyeglasses and in the shells of bicycle helmets. A polycarbonate is made from the reaction of bisphenol A (BPA) with phosgene:
Phenol (C6H5OH) is used to terminate the polymer (stop its growth).
In 1994 chemists at Texas A\&M University reported the synthesis of a non-naturally occurring amino acid:
a. To which naturally occurring amino acid is this compound most similar?
b. A tetrapeptide, phe-met-arg-phe-is synthesized in the brains of rats addicted to morphine and heroin. (Theindicates that the peptide ends ininstead of.) The TAMU
scientists synthesized a similar tetrapeptide, with the synthetic amino acid above replacing one of the original amino acids. Draw a structure for the tetrapeptide containing the synthetic amino acid.
c. Indicate the chiral carbon atoms in the synthetic amino acid.
d. Draw the geometric isomers for this synthetic amino acid. (Hint: Refer to Exercise 25.)
Give the structure for each of the following.
a. 3-hexene
b. 2, 4-heptadiene
c. 2-methyl-3-octene
d. 4-methyl-1-pentyne
Consider the titration of 50.0 mL of 1.0 M glycine hydrochloride [(H3NCH2COOH)Cl], with 1.0 M NaOH.For +H3NCH2COOH, Ka for the carboxylic acid groupis and Kb for the amino group is .
a. Calculate the pH after 25.0 mL, 50.0 mL, and75.0 mL of NaOH has been added. Hint: Refer toSection 8.7 of the text, and treat the titration of+H3NCH2COOH as a diprotic acid titration.
b. Sketch the titration curve and indicate the majoramino acid species present after 0.0 mL, 25.0 mL,50.0 mL, 75.0 mL, and 100.0 mL of 1.0 M NaOHhave reacted completely. Assume the initial pH is1.2 and the pH at the second equivalence pointis 11.7.
c. At what pH do the majority of amino acid molecules have a net charge of zero? This pH is calledthe isoelectric point.
d. At what pH is the net charge of the major aminoacid species present equal to
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