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chemistry
organic chemistry
Questions and Answers of
Organic Chemistry
Assign R or S stereochemistry to the chirality centers in the following Newmanprojections:
Xylose is a common sugar found in many types of wood, including maple and cherry. Because it is much less prone to cause tooth decay than sucrose, xylose has been used in candy and chewing gum.
Ribose, an essential part of ribonucleic acid (RNA), has the following structure: (a) How many chirality centers does ribose have? Identify them. (b) How many stereo isomers of ribose are there? (c)
On catalytic hydrogenation over a platinum catalyst, ribose (Problem 9.57) is converted into ribitol. Is ribitol optically active or inactive?Explain.
Hydroxylation of cis-2-hutene with OsO4 yields 2, 3-butanediol. What stereochemistry do you expect for the product?
Hydroxylation of trans-2-butene with OsO4 also yields 2, 3-butanediol. What stereochemistry do you expect for the product?
Cis-4-Octene reacts with a peroxyacid to yield 4, 5-epoxyoctane. Is the product chiral? How many chirality centers does it have? How would you describe it stereo chemically?
Answer Problem 9.61 for the epoxidation of trans-4-octene.
Identify the indicated hydrogen’s in the following molecules as pro-R or pro-S:
Identify the indicated faces in the following molecules as Re orSi:
Draw all possible stereo isomers of 1, 2-cyclobutanedicarboxylic acid, and indicate the interrelationships. Which, if any, are optically active? Do the same for 1, 3-cyclohutanedicarhoxylic acid.
Compound A, C7H12, was found to be optically active. On catalytic reduction over a palladium catalyst, 2 equivalents of hydrogen were absorbed, yielding compound B, C7H16. On ozonolysis of A, two
Compound A, C11H160, was found to be an optically active alcohol. Despite its apparent unsaturation, no hydrogen was absorbed on catalytic reduction over a palladium catalyst. On treatment of A with
One of the steps in fat metabolism is the hydration of crotonate to yield 3-hydroxybutyratc. The reaction occurs by addition of —OH to the Si face at C3, followed by Protonation at C2, also from
The dehydration of citrate to yield cis-aconitate, a step in the citric acid cycle, involves the pro-R ?arm? of citrate rather than the pro-S arm. W1ich of the following two products is formed?
The first step in the metabolism of glycerol formed by digestion of fats is phosphorylation of the pro-R – CH2OH group by reaction with All’ to give the corresponding glycerol phosphate. Show the
One of the steps in fatty-acid biosynthesis is the dehydration of (R)-3-hydroxy-butyryl ACP to give trans-crotonyl ACP. Does the reaction remove the pro-R or the pro-S hydrogen fromC2?
Allenes are compounds with adjacent carbon—carbon double bonds. Many allenes are chiral, even though they don’t contain chirality centers. Mycomycin, for example, a naturally occurring antibiotic
Long before chiral allenes were known (Problem 9.72), the resolution of 4-methylcyclohexylideneacetic acid into two enantiomers had been carried out. Why is it chiral? What geometric similarity does
(S)-i-Chloro-2-mcthylbutane undergoes light-induced reaction with Cl2 by a radical mechanism to yield a mixture of products, among which are 1, 4-dichloro-2-methylbutanc and 1,
Draw the structure of a meso compound that has five carbons and three chirality centers.
How many stereo isomers of 2, 4-dibromo-3-chloropentane are there? Draw them, and indicate which are optically active.
Draw both cis- and trans-i, 4-dimethylcyclohexane in their most stable chair conformations.(a) How many stereo isomers are there of cis-1, 4-dimethylcyclohexane, and how many of trans- 1,
Draw both cis- and trans-1, 3-dimethylcyclohexane in their most stable chair conformations.(a) How many stereo isomers are there of cis-l, 3-dimethylcyclohcxane, and how many of trans-1,
Cis-1, 2-Dimethylcyclohexane is optically inactive even though it has two chirality centers. Explain.
We’ll see in the next chapter that alkyl halides react with nucleophiles to give substitution products by a mechanism that involves inversion of stereochemistry at carbon: Draw the reaction of
Ketones react with acetylide ion (Section 8.7) to give alcohols. For example, the reaction of sodium acetylide with 2-hutanone yields 3-methyl-l-pentyn-3-ol:(a) Is the product chiral? Is it optically
Imagine that another reaction similar to that in Problem 9.81 is carried out between sodium acetylide and (R)-2-phenylpropanal to yield 1-phenyl- 3-butyn-2-ol:(a) Is the product chiral? Is it
Name the following compounds:
There are seven isomeric alkynes with the formula C6H10. Draw and name them.
What products would you expect from the followingreactions?
What product would you obtain by hydration of the following alkynes?
What alkynes would you start with to prepare the followingketones?
What alkyne would you start with to prepare each of the following compounds by a hydroboration/oxidationreaction?
How would you prepare the following carbonyl compounds starting from an alkyne (reddish brown ? Br)?
Using any alkyne needed, how would you prepare the following alkenes?(a) Trans-2-Octenc(b) Cis-3-Heptcne(c) 3-Methyl-1-pentene
The pKa of acetone, CH3COCH3, is 19.3. Which of the following bases is strong enough to de-protonate acetone?(a) KOH (pKa of H2O = 15.7) (b) Na+ –C ≡ CH (pKa of C2H2 = 25)(c) NaHCO3 (pKa of
Show the terminal alkyne and alkyl halide from which the following products can he obtained. If two routes look feasible, list both.
How would you prepare ds-2-butene starting from propyne, an alkyl halide, and any other reagents needed? This problem can’t be worked in a single step. You’ll have to carry out more than one
Beginning with 4-octyne as your only source of carbon, and using any inorganic reagents necessary, how would you synthesize the following compounds?(a) cis-4-Octene(b) Butanal(c) 4-Bromooctane(d)
Beginning with acetylene and any alkyl halides needed, how would you synthesize the following compounds?(a) Decane(b) 2, 2-Dimethylhexane(c) Hexanal(d) 2-Heptanone
Name the following alkynes, and predict the products of their reaction with (i) H2 in the presence of a Lindlar catalyst and (ii) H3O+ in the presence ofHgSO4:
From what alkyne might each of the following substances have been made? (Yellow-green =Cl)
How would you prepare the following substances, starting from any corn- pounds having four carbons orfewer?
The following cyloalkyne is too unstable to exist.Explain.
Give IUPAC names for the followingcompounds:
Draw structures corresponding to the following names:(a) 3, 3-Dimethyl-4-octyne(b) 3-Ethyl-5-methyl- 1, 6, 8-decatriyne(c) 2, 2, 5, 5-TetramethyL-3-hexyne(d) 3, 4-Dimethylcyclodecyne(e) 3,
The following two hydrocarbons have been isolated from various plants in the sunflower family. Name them according to IUPAC rules.(a) CH3CH = CHC ≡ CC ≡ CCH = CHCH = CHCH = CH2 (all trails)(b)
Predict the products of the followingreactions:
A hydrocarbon of unknown structure has the formula C8H10. On catalytic hydrogenation over the Lindlar catalyst, 1 equivalent of H2 is absorbed. On hydrogenation over a palladium catalyst, 3
Predict the products from reaction of 1-hexyne with the following reagents:(a) 1 equiv HBr(b) 1 equiv Cl2(c) H2, Lindlar catalyst(d) NaNH2 in NH3, then CH3Br(e) H2O, H2SO4, HgSO4(f) 2 equiv HC1
Predict the products from reaction of 5-decyne with the following reagents:(a) H2 Lindlar catalyst(b) Li in NH3(c) 1 equiv Br2(d) BH3 in THF, then H2O2, OH–(c) H2O, H2SO4, HgSO4(f) Excess H2, Pd/C
Predict the products from reaction of 2-hexyne with the following reagents:(a) 2 equiv Br2(b) 1 equiv HBr(c) Excess HBr(d) Li in NH3(e) H2O, H2SO4, HgSO4
How would you carry out the following conversions? More than one step may be needed is some instances.
Hydrocarbon A has the formula C9H12 and absorbs 3 equivalents of H2 to yield R, C9H18, when hydrogenated over a Pd/C catalyst. On treatment of A with aqueous H2SO4 in the presence of mercury (II),
How would you carry out the followingreactions?
Occasionally, chemists need to invert the stereochemistry of an alkene?that is, to convert a cis alkene to a trans alkene, or vice versa. There is no one-step method for doing an alkene inversion,
Propose structures for hydrocarbons that give the following products on oxidative cleavage by KMnO4 orO3:
Each of the following syntheses requires more than one step. How would you carry themout?
How would you carry out the following transformation? More than one step isneeded.
How would you carry out the following conversions? More than one step is needed in eachcase.
Synthesize the following compounds using 1-butyne as the only source of carbon, along with any inorganic reagents you need. More than one step may be needed.(a) 1, 1, 2, 2-Tetrachlorobutane(b) 1, 1
How would you synthesize the following compounds from acetylene and any alkyl halides with four or fewer carbons? More than one step may herequired.
How would you carry out the following reactions to introduce deuterium into organicmolecules?
How would you prepare Cyclodecyne starting from acetylene and any alkyl halide needed?
The sex attractant given off by the common housefly is an alkene named muscalure. Propose a synthesis of muscalure starting from acetylene and any alkyl halides needed. What is the IUPAC name
Compound A (C9H12) absorbed 3 equivalents of H2 on catalytic reduction over a palladium catalyst to give L (C9H18). On ozonolysis, compound A gave, among other things, a ketone that was identified as
Hydrocarbon A has the formula C12H8. It absorbs 8 equivalents of H2 on catalytic reduction over a palladium catalyst. On ozonolysis, only two products are formed: oxalic acid (HO2CCO2H) and succinic
Identify the reagents a?c in the following scheme:
Organo metallic reagents such as sodium acetylide undergo an addition reaction with ketones, giving alcohols: How might you use this reaction to prepare 2-methyl-1, 3-butadiene, the starting material
The oral contraceptive agent Mestranol is synthesized using a carbonyl addition reaction like that shown in Problem 8.42. Draw the structure of the ketoneneeded.
Erythrogenic acid, C18H26O2, is an acetylenic fatty acid that turns a vivid red on exposure to light. On catalytic hydrogenation over a palladium catalyst, 5 equivalents of H2 is absorbed, and
Terminal alkynes react with Br2 and water to yield bromo ketones. For example: Propose a mechanism for the reaction. To what reaction of alkenes is the processanalogous?
A cumulene is a compound with three adjacent double bonds. Draw an orbital picture of a cumulene. What kind of hybridization do the two central carbon atoms have? What is the geometric relationship
Reaction of acetone with D3O+ yields hexadeuterioacetone. That is, all the hydrogen?s in acetone are exchanged for deuterium. Review the mechanism of mercuric ion?catalyzed alkyne hydration, arid
Give IUPAC names for the following alkylhalides:
Draw structures corresponding to the following IUPAC names:(a) 2-Chloro-3, 3-dimethylhexane(b) 3, 3-Dichloro-2-methylhexane(c) 3-Bromo-3-ethylpentane(d) 1, 1-Dibromo-4-isopropylcyclohexane(e)
Draw and name all monochloro products you would expect to obtain from radical chlorination of 2-methylpentane. Which, if any, are chiral?
Taking the relative reactivities of 1o, 2o, and 3o hydrogen atoms into account, what product(s) would you expect to obtain from monochlorination of 2-methylbutane? What would the approximate
Draw three resonance forms for the cyclohexadienylradical.
The major product of the reaction of methylenecyclohexane with N-bromo-succinimide is 1-(bromomethyl) cyclohexane. Explain
What products would you expect from reaction of the following alkenes with NBS? If more than one product is formed, show the structures ofall.
How would you prepare the following alkyl halides from the correspondingalcohols?
How strong a base would you expect a Grignard reagent to be? Look at Table 8.1, and then predict whether the following reactions will occur as written.?(The pKa of NH3 is 35.) (a) CH3MgBr + H ? C ? C
How might you replace a halogen substituent by a deuterium atom if you wanted to prepare a deuteratedcompound?
How would you carry out the following transformations using an organo copper coupling reaction? More than one step is required in eachcase.
Rank each of the following series of compounds in order of increasing oxidationlevel:
Tell whether each of the following reactions is an oxidation, a reduction, orneither.
Give a JUPAC name for each of the following alkyl halides (yellow green =Cl):
Show the product(s) of reaction of the following alkenes withNBS:
The following alkyl bromide can be prepared by reaction of the alcohol (S)-2-pentanol with PBr3. Name the compound, assign (R) or (S) stereochemistry, and tell whether the reaction of the alcohol
Name the following alkylhalides:
Draw structures corresponding to the following IUPAC names:(a) 2, 3-Dichloro-4-methylhexane(b) 4-Bromo-4-ethyl-2-methylhexane(c) 3-Iodo-2, 2, 4, 4-tetramethylpentane(d) cis- 1
Draw and name the monochlorination products you might obtain by radical chlorination of 2-methylbutane. Which of the products are chiral? Are any of the products optically active?
A chemist requires a large amount of 1-bromo-2-pentene as starting material for a synthesis and decides to carry out an NBS allylic bromination reaction. What is wrong with the following synthesis
What product(s) would you expect from the reaction of 1-methylcyclohexene with NBS? Would you use this reaction as part of asynthesis?
How would you prepare the following compounds, starting with cyclopentane and any other reagents needed?(a) Chloro cyclopentane(b) Methylcyclopentane(c) 3-Bromocyclopentene(d) Cyclopentanol(e)
Predict the product(s) of the followingreactions:
(S)-3-Methylhexane undergoes radical bromination to yield optically inactive 3-hromo-3-methylhexane as the major product. Is the product chiral? What conclusions can you draw about the radical
Assume that you have carried out a radical chlorination reaction on (R)-2-chloro- pentane and have isolated (in low yield) 2, 4-dichioropentane. How many stereoisomers of the product are formed and
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