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organic chemistry

Questions and Answers of Organic Chemistry

Compound X is a d-aldohexose that can adopt a β-pyranose form with only one axial substituent. Compound X undergoes a Wohl degradation to produce an aldopentose, which is converted into an optically
Compound A is a d-aldopentose. When treated with sodium borohydride, compound A is converted into an alditol that exhibits three signals in its 13C NMR spectrum. Compound A undergoes a
Although most naturally occurring proteins are made up only of l amino acids, proteins isolated from bacteria will sometimes contain d amino acids. Draw Fischer projections for d-alanine and
Draw a bond-line structure for each of the following amino acids.(a) l-Leucine (b) l-Tryptophan(c) l-Methionine (d) l-Valine
Of the 20 naturally occurring amino acids shown in the following table, identify any amino acids that exhibit the following:(a) A cyclic structure (b) An aromatic side chain(c) A side chain with a
Draw the form of the amino acid that is expected to predominate at the stated pH.(a) Alanine at a pH of 10 (b) Proline at a pH of 10(c) Tyrosine at a pH of 9 (d) Asparagine at physiological
At a pH of 11, arginine is a more effective proton donor than asparagine. Explain.
Explain why it is inappropriate to use a chiral catalyst in the preparation of glycine.
The OH group on the side chain of serine is not deprotonated at a pH of 12. However, the OH group on the side chain of tyrosine is deprotonated at a pH of 12. This can be verified by inspecting the
Using the data in the following table, calculate the pI of the following amino acids.(a) Aspartic acid (b) Leucine(c) Lysine (d) Proline THE PK,VALUES FOR TWENTY NATURALLY OCCURRING AMINO
For each group of amino acids, identify the amino acid with the lowest pI (try to solve this problem by inspecting their structures, rather than performing calculations).(a) Alanine, aspartic acid,
Identify which 2 of the 20 naturally occurring amino acids are expected to have the same pI.
A mixture containing phenylalanine, tryptophan, and leucine was subjected to electrophoresis. Determine which of the amino acids moved the farthest distance assuming that the experiment was performed
Identify the starting alkene necessary to make each of the following amino acids using an asymmetric catalytic hydrogenation.(a) l-alanine (b) l-valine(c) l-leucine (d) l-tyrosine
Draw the aldehyde that is obtained as a byproduct when l-leucine is treated with ninhydrin.
Identify the reagents necessary to make each of the following amino acids using a Hell‑Volhard‑Zelinski reaction.(a) Leucine (b) Alanine (c) Valine
Each of the following aldehydes was converted into an α-amino nitrile followed by hydrolysis to yield an amino acid. In each case, draw and name the amino acid that was produced.(a)
Each of the following carboxylic acids was treated with bromine and PBr3 followed by water, and the resulting Î±-haloacid was then treated with excess ammonia. In each case, draw and
Identify the reagents necessary to make each of the following amino acids via the amidomalonate synthesis.(a) Isoleucine (b) Alanine (c) Valine
An amidomalonate synthesis was performed using each of the following alkyl halides. In each case, draw and name the amino acid that is produced.(a) Methyl chloride (b) Isopropyl
Both leucine and isoleucine can be prepared via the amidomalonate synthesis, although one of these amino acids can be produced in higher yields. Identify the higher yield process and explain your
Identify the reagents necessary to make each of the following amino acids using a Strecker synthesis.(a) Methionine (b) Histidine(c) Phenylalanine (d) Leucine
Draw a mechanism for the following transformation: ОН Но но. но Он он HCI ОН Но но- ОН
Salicin is a natural analgesic present in the bark of willow trees, and it has been used for thousands of years to treat pain and reduce fevers.(a) Is salicin a reducing sugar?(b) Identify the
Isomaltose is similar in structure to maltose, except that it is a 1→6 α-glycoside, rather than a 1→4 α-glycoside. Draw the structure of isomaltose.
Xylitol is found in many kinds of berries. It is approximately as sweet as sucrose but with fewer calories. It is often used in sugarless chewing gum. Xylitol is obtained upon reduction of d xylose.
Trehalose is a naturally occurring disaccharide found in bacteria, insects, and many plants. It protects cells from dry conditions because of its ability to retain water, thereby preventing cellular
Consider the structures of the four d-aldopentoses (See the following figure).(a) Which d-aldopentose produces the same aldaric acid as d-lyxose?(b) Which d-aldopentoses yield optically inactive
Identify the product(s) that would be formed when each of the following compounds is treated with aqueous acid:(a) Methyl α-d-glucopyranoside (b) Ethyl β-d-galactopyranoside
Identify the reagents that you would use to convert Î²-d-glucopyranose into each of the following compounds:(a)(b)(c)(d) CH,OH но- Но- -ОСН ОН ноСH оСHз Он но Но Он
Determine whether each of the following compounds is a reducing sugar: CH,OH CH-он Но -ОСН но но- он ОН Он Он
Which of the d-aldohexoses are converted into optically inactive alditols upon treatment with sodium borohydride?
When treated with sodium borohydride, d-glucose is converted into an alditol.(a) Draw the structure of the alditol.(b) Which l-aldohexose gives the same alditol when treated with sodium borohydride?
Identify the two products obtained when d-glyceraldehyde is treated with HCN, and determine the relationship between these two products.
Identify the two aldohexoses that are obtained when d-arabinose undergoes a Kiliani-Fischer synthesis.
Identify the two aldohexoses that will undergo a Wohl degradation to yield d-ribose. Draw a Fischer projection of the open-chain form for each of these two aldohexoses.
Draw all possible 2-ketohexoses that are d sugars.
For each of the following pairs of compounds, determine whether they are enantiomers, epimers, diastereomers that are not epimers, or identical compounds:(a) d-Glucose and d-gulose(b)
Draw the products that are expected when α-dgalactopyranose is treated with excess methyl iodide in the presence of silver oxide, followed by aqueous acid.
Draw the more stable chair conformation of α-daltropyranose and label all substituents as axial or equatorial.
In addition to d-galactose, one other d-aldohexose also forms an optically inactive aldaric acid when treated with nitric acid. Draw the structure of this aldohexose.
When d-galactose is heated in the presence of nitric acid, an optically inactive compound is obtained. Draw the structure of the product and explain why it is optically inactive.
Draw the products that are expected when β-dallopyranose is treated with each of the following reagents:(a) Excess CH3I, Ag2O(b) Excess acetic anhydride, pyridine(c) CH3OH, HCl
Draw the open-chain form of each of the compounds in the previous problem.In previous problem(a)(b)(c) CH,OH Но- Он ОН Он НОСH Но Он ОН Он
Provide a complete name for each of the following compounds:(a)(b)(c) CH,OH Но- Он ОН Он НОСH Но Он ОН Он
Draw a Haworth projection showing the α-pyranose form of the d-aldohexose that is epimeric with d-glucose at C3.
Identify each of the following structures as either d- or l-glyceraldehyde:(a)(b)(c)(d) Но H. ОН н ОН ОН
Name each of the following aldohexoses:(a)(b)(c)(d) н Н- -ОН -н Но -он ОН Н- -он ОН Н ČH,OH Н. но- -н Но- -н Н -ОН Н -ОН ČH,OH
Consider the structures of the d aldopentoses:(a) Identify the aldopentose that is epimeric with d-arabinose at C2.(b) Identify the aldopentose that is epimeric with d-lyxose at C3.(c) Draw the
Draw the cyclic hemiacetal that is formed when each of the following bifunctional compounds is treated with aqueous acid.(a)(b)(c) но. НО H. но
Identify the hydroxyaldehyde that will cyclize under acidic conditions to give the following hemiacetal: -OH
D-Ribose can adopt two pyranose forms and two furanose forms.(a) Draw both pyranose forms of d-ribose, and identify each as α or β.(b) Draw both furanose forms of d-ribose, and identify each as α
For each of the following pairs of compounds, determine whether they are enantiomers, epimers, diastereomers that are not epimers, or identical compounds:(a)(b)(c)(d) Н Н. O: Н ОН но н Но-
Draw the open-chain form of the compound formed when methyl β-d-glucopyranoside is treated with aqueous acid.
Assign the configuration of each chirality center in the following compounds:(a)(b)(c)(d)(e) C=0 Н- -ОН Н -Он ČH,OH Н %3D Н- -ОН н —Он но- —н ČH,OH
Draw a Fischer projection for each of the following compounds:(a) d-glucose(b) d-galactose(c) d-mannose(d) d-allose
Draw a Haworth projection for each of the following compounds:(a) β-d-Fructofuranose(b) β-d-Galactopyranose(c) β-d-Glucopyranose(d) β-d-Mannopyranose
Classify each of the following monosaccharides as either d or l, as either an aldo or a keto sugar, and as a tetrose, pentose, or hexose:(a)(b)(c)(d)(e) Н. C=0 Н. -он -он CH-он 12 エエ
Predict the product that is obtained when cellobiose is treated with each of the following reagents:(a) NaBH4, H2O(b) Br2, H2O (pH = 6)(c) CH3OH, HCl(d) Ac2O, pyridine
Draw the structure of the product obtained when the following disaccharide is treated with NaBH4in methanol. CH-Он CH-ОН Но Но- ОН но- ОН ОН
Determine whether each of the following disaccharides is a reducing sugar.(a)(b)(c) CH,OH HO CH,OH Но. ОН но. -OH OH
When d-glucose undergoes a Wohl degradation followed by a Kiliani-Fischer chain-lengthening process, a mixture of two epimeric products are obtained. Identify both epimers.
Identify the reagents you would use to convert d-ribose into d-erythrose.
Draw and name the two aldohexoses that can be converted into d-ribose using a Wohl degradation.
Identify the reagents you would use to convert d-erythrose into d-ribose. What other product is also formed in this process?
Draw and name the pair of epimers formed when the following aldopentoses undergo a Kiliani Fischer chain-lengthening process:(a)(b)(c) Н. %3D Н -Он Н. -ОН Н- -он CH-ОН D-Ribose Н. %3D
Do you expect β-d-Glucopyranose pentamethyl ether to be a reducing sugar? Explain your reasoning.
Draw and name the product obtained when each of the following compounds is treated with aqueous bromine (at pH = 6):(a) α-d-Galactopyranose (b) β-d-Galactopyranose(c)
Determine whether each of the following compounds is a reducing sugar:(a)(b)(c) CH,OH но- ОН ÓCH, Он ОН сH-Он Но. ОН ОН
Of the eight d-aldohexoses, only two of them form optically inactive alditols when treated with sodium borohydride in the presence of water. Identify these two aldohexoses and explain why their
The same product is obtained when either d-allose or l-allose is treated with sodium borohydride in the presence of water. Explain this observation.
The same product is obtained when either d-altrose or d-talose is treated with sodium borohydride in the presence of water. Explain this observation.
Draw and name the structure of the aldohexose that is epimeric with d-glucose at each of the following positions:(a) C2 (b) C3 (c) C4
Methyl α-d-glucopyranoside is a stable compound that does not undergo mutarotation under neutral or basic conditions. However, when subjected to acidic conditions, an equilibrium is established
When α-d-galactopyranose is treated with ethanol in the presence of an acid catalyst, such as HCl, two products are formed. Draw both products, and account for their formation with a mechanism.
Draw the product obtained when each of the compounds from the previous problem is treated with methyl iodide in the presence of silver oxide (Ag2O).In previous problem(a)
Draw the product obtained when each of the following compounds is treated with acetic anhydride in the presence of pyridine:(a) α-d-Galactopyranose (b) α-d-Glucopyranose(c) β-d-Galactopyranose
Draw the open-chain form of the carbohydrate that can undergo acid-catalyzed cyclization to produce α-dfructopyranose.
Draw a mechanism for the acid-catalyzed cyclization of d-fructose to give β-d-fructofuranose.
Draw a mechanism for the acid-catalyzed cyclization of l-threose to give β-l-threofuranose.
Consider the structures of the following two d-aldotetroses:Each of these compounds exists as a furanose ring, which is formed when the OH at C4 attacks the aldehyde moiety. Draw each of the
There are two chair conformations for β-d-glucopyranose. Draw the less stable chair conformation.
Draw the open-chain form of the following cyclic monosaccharide: CH,OH но- ОН ОН ОН
Draw the more stable chair conformation for each of the following compounds:(a) β-d-Galactopyranose (b) α-d-Glucopyranose (c) β-d-Glucopyranose
When d-talose is dissolved in water, an equilibrium is established in which two pyranose forms are present. Draw both pyranose forms and name them.
Mutarotation causes the conversion of b-d-mannopyranose to α-d-mannopyranose. Using Haworth projections, draw the equilibrium between the two pyranose forms and the open-chain form of d-mannose.
Provide a complete name for the following compound: CH-ОН ОН ОН н Н ОН н Н Н ОН
Draw a Haworth projection for each of the following compounds:(a) β-d-Galactopyranose (b) α-d-Mannopyranose (c) α-d-Allopyranose(d) β-d-Mannopyranose (e) β-d-Glucopyranose (f
The following compound has one aldehyde group and two OH groups: Under acidic conditions, either one of the OH groups can function as a nucleophile and attack the carbonyl group, giving rise to two
Identify the hydroxyaldehyde that will cyclize under acidic conditions to give the following hemiacetal: -OH
Draw the cyclic hemiacetal that is formed when each of the following bifunctional compounds is treated with aqueous acid:(a)(b)(c)(d) н Он Но H.
Which of the following terms best describes the relationship between d-fructose and d-glucose? Explain your choice.(a) Enantiomers(b) Diastereomers(c) Constitutional isomers
D-allose is an aldohexose in which all four chirality centers have the R configuration. Draw a Fischer projection of each of the following compounds:(a) d-Allose(b) l-Allose.
Determine whether each of the following carbohydrates is a d sugar or an l sugar, and assign a configuration for each chirality center. After assigning the configuration for all of the
Would you expect an aldohexose and a ketohexose to be constitutionally isomeric? Explain why or why not.
Classify each of the following carbohydrates as an aldose or ketose, and then insert the appropriate term to indicate the number of carbon atoms present (e.g., an aldopentose):(a)(b)(c)(d)(e) H. HO
Draw and name the enantiomer of d-fructose.
There are only two stereoisomeric ketotetroses.(a) Draw both of them.(b) Identify their stereoisomeric relationship.(c) Identify which is a d sugar and which is an l sugar.
There are four stereoisomeric aldotetroses.(a) Draw all four, and arrange them in pairs of enantiomers.(b) Identify which stereoisomers are d sugars and which are l sugars.
How would you use IR spectroscopy to distinguish between the following pairs of compounds?(a)(b) N.

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