Organic Chemistry 2nd Edition solutions

Organic Chemistry 2
Draw a bond-line structure showing the zwitterionic form of each of the following amino acids: (a) l- Valine (b) l-Tryptophan (c) l-Glutamine (d) l-Proline

Organic Chemistry 2
The 20 naturally occurring amino acids (Table 25.1) are all l amino acids, and they all have the S configuration, with the exception of glycine (which lacks a chirality center) and cysteine. Naturally occurring cysteine is an l amino acid, but it has the R configuration. Explain.

Organic Chemistry 2
Draw a Fischer projection for each of the following amino acids: (a) l-Threonine (b) l-Serine (c) l- Phenylalanine (d) l-Asparagine

Organic Chemistry 2
Seventeen of the 20 naturally occurring amino acids (Table 25.1) exhibit exactly one chirality center. Of the remaining three amino acids, glycine has no chirality center, and the other two amino acids each have two chirality centers. (a) Identify the amino acids with two chirality centers. (b) Assig

Organic Chemistry 2
Draw all stereoisomers of l-isoleucine. In each stereoisomer, assign the configuration (R or S) of all chirality centers.

Organic Chemistry 2
Arginine is the most basic of the 20 naturally occurring amino acids. At physiological pH, the side chain of arginine is protonated. Identify which nitrogen atom in the side chain is protonated. (Hint: Consider all three possibilities and draw all resonance structures.)

Organic Chemistry 2
Histidine possesses a basic side chain which is protonated at physiological pH. Identify which nitrogen atom in the side chain is protonated.

Organic Chemistry 2
Draw the form of l-glutamic acid that predominates at each pH: (a) 1.9 (b) 2.4 (c) 5.8 (d) 10.4

Organic Chemistry 2
For each of the following amino acids, draw the form that is expected to predominate at physiological pH: (a) l-Isoleucine (b) l-Tryptophan (c) l-Glutamine (d) l-Glutamic acid

Organic Chemistry 2
Using the data in Table 25.2, calculate the pI of the following amino acids: (a) l-Alanine (b) l- Asparagine (c) l-Histidine (d) l-Glutamic acid

Organic Chemistry 2
Just as each amino acid has a unique pI value, proteins also have an overall observable pI. For example, lysozyme (present in tears and saliva) has a pI of 11.0 while pepsin (used in our stomachs to digest other proteins) has a pI of 1.0. What information does this give you about the types of amino a

Organic Chemistry 2
For each amino acid, draw the structure that predominates at the isoelectric point: (a) l-Glutamine (b) l-Phenylalanine (c) l-Proline (d) l-Threonine

Organic Chemistry 2
Optically active amino acids undergo racemization at the a position when treated with strongly basic conditions. Provide a mechanism that supports this observation.

Organic Chemistry 2
A mixture containing glycine, l-glutamine, and l-asparagine was subjected to electrophoresis. Identify which of the amino acids moved the farthest distance assuming that the experiment was performed at the pH indicated: (a) 6.0 (b) 5.0

Organic Chemistry 2
Draw the products that are expected when each of the following amino acids is treated with ninhydrin: (a) l-Aspartic acid (b) l-Leucine (c) l-Phenylalanine (d) l-Proline

Organic Chemistry 2
A mixture of amino acids was treated with ninhydrin, and the following aldehydes were all observed in the product mixture: S H O O H H H O (a) Identify the structure and name all three amino acids in the starting mixture. (b) In addition to the aldehydes, a purple-colored product is obtained. Draw th

Organic Chemistry 2
Show how you would use a Strecker synthesis to make valine.

Organic Chemistry 2
Under similar conditions, alanine and valine were each prepared with an amidomalonate synthesis, and alanine was obtained in higher yields than valine. Explain the difference in yields.

Organic Chemistry 2
The amidomalonate synthesis can be used to prepare amino acids from alkyl halides. When the amidomalonat

Organic Chemistry 2
Predict the major product(s) in each of the following cases: OH O 1) Br2, PBr3 2) H2O 3) Excess NH3 ? (a) 1) NH4Cl, NaCN 2) H3O+ H (b) O ? EtO OEt O O N O H 1) NaOEt 2) CH3I 3) H3O+, heat ? (c)

Organic Chemistry 2
Show how racemic valine can be prepared by each of the following methods: (a) The Hell-Volhard- Zelinsky reaction (b) The amidomalonate synthesis (c) The Strecker synthesis

Organic Chemistry 2
How many different pentapeptides can be constructed from the 20 naturally occurring amino acids in Table 25.1?

Organic Chemistry 2
Using an asymmetric catalytic hydrogenation, identify the starting alkene that you would use to make l-histidine.

Organic Chemistry 2
Using three-letter abbreviations, identify all possible acyclic tripeptides containing l-leucine, l- methionine, and l-valine.

Organic Chemistry 2
Draw the predominant form of Asp-Lys-Phe at physiological pH

Organic Chemistry 2
Draw a bond-line structure of the peptide that corresponds with the following sequence of amino acid residues and identify the N terminus and C terminus: Trp-Val-Ser-Met-Gly-Glu

Organic Chemistry 2
Methionine enkephalin is a pentapeptide that is produced by the body to control pain. From the sequence of its amino acid residues, draw a bond-line structure of methionine enkephalin. Tyr Gly Gly Phe Met Methionine enkephalin N terminus C terminus

Organic Chemistry 2
From its amino acid sequence, draw the form of aspartame that is expected to predominate at physiological pH: Asp-Phe-OCH3

Organic Chemistry 2
t is believed that penicillin antibiotics are biosynthesized from amino acid precursors. Identify the two amino acids that are most likely utilized during the biosynthesis of penicillin antibiotics: N O N S COOH H

Organic Chemistry 2
Green fluorescent protein (GFP), first isolated from bioluminescent jellyfish, is a protein containing 238 amino acid residues. The discovery of GFP has revolutionized the field of fluorescence microscopy, which enables biochemists to monitor the biosynthesis of proteins. The 2008 Nobel Prize in Chem

Organic Chemistry 2
Propose two structures for a tripeptide that contains glycine, l-alanine, and l-phenylalanine but does not react with phenyl isothiocyanate.

Organic Chemistry 2
Bradykinin has the following sequence: (N terminus) Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg (C terminus) Identify all fragments that will be produced when bradykinin is treated with: (a) Trypsin (b) Chymotrypsin

Organic Chemistry 2
Identify the N-terminal residue of a peptide that yields the following PTH derivative upon Edman degradation: HN N O S

Organic Chemistry 2
Treatment of a tripeptide with phenyl isothiocyanate yields compound A and a dipeptide. Treatment of the dipeptide with phenyl isothiocyanate yields compound B and glycine. Identify the structure of the starting tripeptide. HN N O S Compound A HN N O S Compound B

Organic Chemistry 2
Glucagon is a peptide hormone produced by the pancreas that, with insulin, regulates blood glucose levels. Glucagon is comprised of 29 amino acid residues. Treatment with trypsin yields four fragments, while treatment with chymotrypsin yields six fragments. Identify the sequence of amino acid residue

Organic Chemistry 2
When the N terminus of a peptide is acetylated, the peptide derivative that is formed is unreactive toward phenyl isothiocyanate. Explain. N H H PEPTIDE Acetylation N H PEPTIDE O

Organic Chemistry 2
Predict the major product(s) of the reaction between l-valine and: (a) MeOH, H+ (b) Di-tert-butyl- dicarbonate (c) NaOH, H2O (d) HCl

Organic Chemistry 2
Show all steps necessary to make the dipeptide Phe-Ala from l-phenylalanine and l-alanine.

Organic Chemistry 2
Draw all four possible dipeptides that are obtained when a mixture of l-phenylalanine and l-alanine is treated with DCC.

Organic Chemistry 2
Identify the steps you would use to combine Val-Leu and PheIle to form the tetrapeptide Phe-Ile-Val- Leu.

Organic Chemistry 2
Identify all of the steps necessary to prepare the tripeptide LeuVal-Ala with a Merrifield synthesis.

Organic Chemistry 2
Draw the structure of the protected amino acid that must be anchored to the solid support in order to use a Merrifield synthesis to prepare leucine enkephalin. (N terminus) Try-Gly-Gly-Phe-Leu (C terminus)

Organic Chemistry 2
A proline residue will often appear at the end of an a helix but will rarely appear in the middle. Explain why proline generally cannot be incorporated into an a helix.

Organic Chemistry 2
Draw a mechanism for the following reaction: OH O H2N OH O H O N O O O O O O

Organic Chemistry 2
Draw the alkyl halide that would be necessary to make the amino acid tyrosine using an amidomalonate synthesis. This alkyl halide is highly susceptible to polymerization. Draw the structure of the expected polymeric material.

Organic Chemistry 2
When leucine is prepared with an amidomalonate synthesis, isobutylene (also called 2- methylpropene) is a gaseous by-product. Draw a mechanism for the formation of this by-product.

Organic Chemistry 2
The side chain of tryptophan is not considered to be basic, despite the fact that it possesses a nitrogen atom with a lone pair. Explain.

Organic Chemistry 2
Consider a process that attempts to prepare tyrosine using a Hell-Volhard-Zelinsky reaction: (a) Identify the necessary starting carboxylic acid. (b) When treated with Br2, the starting carboxylic acid can react with two equivalents to produce a compound with molecular formula C9H8Br2O3, in which nei

Organic Chemistry 2
Proton NMR spectroscopy provides evidence for the restricted rotation of a peptide bond. For example, N,N-dimethylformamide exhibits three signals in its proton NMR spectrum at room temperature. Two of those signals are observed upfield, at 2.9 and 3.0 ppm. As the temperature is raised, the two signa

Organic Chemistry 2
We saw in Section 25.6 that DCC can be used to form a peptide bond. We explored the mechanism, and we saw that DCC activates the COOH group so that it readily undergoes nucleophilic acyl substitution. An alternative method for activating a COOH group involves converting it into an activated ester, su

Organic Chemistry 2
When the following compound is treated with concentrated HCl at 100C for several hours, hydrolysis occurs, producing one of the 20 naturally occurring amino acids. Identify which one. O H2N O