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chemistry
organic chemistry
Questions and Answers of
Organic Chemistry
Propose a stereocontrolled synthesis of cis-l-acetoxy-3-methylcyclopentane (margin), starting from trans-1 -chloro-3-methylcyclopentane.
The two seemingly similar reactions shown below differ in their outcomes.The first proceeds in high yield. The yield of the product in the second, however, is diminished by the formation of
Write all possible El products of each reaction in Problem 25.
Formulate the complete step-by-step mechanisms for all the El processes that you identified in Problem 38.
Write the products of the following elimination reactions. Specify the predominant mechanism (El or E2) and formulate it in detail.(a)(b) (c) (d)
From the list of reagents (a)-(f) below, choose all those that are most likely to give primarily (i) SN2 reaction with primary RX; (ii) E2 reaction with primary RX; (iii) SN2 reaction with secondary
Predict the major product(s) that should form from reaction between 1-bromobutane and each of the following substances. By which reaction mechanism is each formed-SN1, SN2, El, or E2? If it appears
Predict the major product(s) and mechanism(s) for reaction between 2-bromobutane (sec-butyl bromide) and each of the reagents in Problem 42. (a) KCl in DMF (b) KI in DMF (c) KC1 in CH3NO2 (d) NH3 in
Predict the major product(s) and mechanism(s) for reaction between 2-bromo-2-methylpropane (tert-butyl bromide) and each of the reagents in Problem 42. (a) KCl in DMF (b) KI in DMF (c) KC1 in
Three reactions of 2-chloro-2-methylpropane are shown here,(a) Write the major product of each transformation(b) Compare the rates of the three reactions. Assume identical solution polarities and
Fill in the blanks in the following table with the major product(s) of the reaction of each haloalkane with the reagents shown.
Indicate the major mechanism(s) (simply specify SN2, SN1, E2, or El) required for the formation of each product that you wrote in Problem 47.
For each of the following reactions, indicate whether the reaction would work well, poorly, or not at all. Formulate alternative products, if appropriate.(a)(b) (c) (d) (e) (f) (g) (h) (i) (j) (k) (l)
Unimolecular elimination to form an alkene accompanies substitution in secondary and tertiary systems.
Propose syntheses of the following molecules from the indicated starting materials. Make use of any other reagents or solvents that you need. In some cases, there may be no alternative but to employ
[(l-Bromo-l-methyl)ethyl]benzene, shown in the margin, undergoes solvohsis in a unimolecular, strictly first-order process. The reaction rate for [RBr] = 0.1 M RBr in 9:1 acetone: water is measured
In this chapter we have encountered many examples of SN1 solvolysis reactions, all of which proceed according to the following scheme:Upon mixing the colorless substrate and solvent, a reddish-orange
Match each of the following transformations to the correct reaction profile shown here, and draw the structures of the species present at all points on the energy curves marked by capital
Formulate the structure of the most likely product of the following reaction of 4-chloro-4-methyl-1-pentanol in neutral polar solution.
The following reaction can proceed through both El and E2 mechanisms.The El rate constant kEI = 1.4 Ã 10-4s-1 and the E2 rate constant kE2 = 1.9 Ã 10-4 L mol-1 s-1; 0.02 M
The compound below is an example of a methyl ester. Methyl esters react with lithium iodide to give lithium carboxylate salts. The solvent in this example is pyridine (margin).Suggest several
Ethers containing the 1,1-dimethylethyl (tert-butyl) group are readily cleaved with dilute, strong acid, as shown in the example below.Suggest a plausible mechanism for this process. What role might
Give the mechanism and major product for the reaction of a secondary haloalkane in a polar aprotic solvent with the following nucleophiles. The pKa value of the conjugate acid of the nucleophile is
Cortisone is an important steroidal anti-inflammatory agent. Cortisone can be synthesized efficiently from the alkene shown here.Of the following three chlorinated compounds, two give reasonable
The chemistry of derivatives of trans-decalin is of interest because this ring system is part of the structure of steroids. Make models of the brominated systems (i and ii) to help you answer the
Which of the following haloalkanes will undergo hydrolysis most rapidly? (a) (CH3)3CF (b) (CH3)3CCl (c) (CH3)3CBr (d) (CH3)3CI
The reactionis an example of which of the following processes? (a) El (b) E2 (c) SN1 (d) SN2
Which reaction intermediate is involved in the following reaction?(a) A secondary radical (b) A tertiary radical (c) A secondary carbocation (d) A tertiary carbocation
Substitution is favored by unhindered substrates and small, less basic nucleophiles.
Draw the structures of the following alcohols, (a) 2-(Trimethylsilyl) ethanol; (b) 1-methylcyclopropanol: (c) 3-( l-methylethyl)-2-hexanol; (d) (R)-2-pentanol; (e) 3,3-dibromocyclohexanol.
Rank each group of compounds in order of increasing boiling point, (a) Cyclohexane, cyclohexanol, chlorocyclohexane; (b) 2,3-dimethyl-2-pentanol, 2-methyl-2-hexanol, 2-heptanol.
Explain the order of water solubilities for the compounds in each of the following groups, (a) Ethanol > chloroethane > ethane; (b) Methanol > ethanol > 1-propanol.
1, 2-Ethanediol exists to a much greater extent in the gauche conformation than does 1, 2-dichloroethane. Explain. Would you expect the gauche: anti conformational ratio of 2-chloroethanol to be
The most stable conformation of trqans-l,2-cyclohexanediol is the chair in which both hydroxy groups are equatorial,(a) Draw the structure or, better yet, make a model of the compound in this
Rank the compounds in each group in order of decreasing acidity. (a) CH3CHCICH20H, CH3CHBrCH2OH, BrCH2CH2CH2OH (b) CH3CH2CH2OH, CCI3CH2OH, (CH3)2CC1CH2OH (c) (CH3)2CHOH, (CF3)2CHOH, (CC13)2CHOH
Write an appropriate equation to show how each of the following alcohols acts as, first, a base, and, second, an acid in solution. How do the base and acid strengths of each compare with those of
Given the pKa values of -2.2 for CH3+OH2 and 15.5 for CH3OH, calculate the pH at which (a) methanol will contain exactly equal amounts of CH3+OH2 and CH3O-; (b) 50% CH3+OH and 50% CH3+OH2 will be
Do you expect hyperconjugation to be important in the stabilization of alkyloxonium ions (e.g., R+OH2, R2+OH)? Explain your answer.
Evaluate each of the following possible alcohol syntheses as being good (the desired alcohol is the major or only product), not so good (the desired alcohol is a minor product), or
For every process in Problem 34 that gives the designated product in poor yield, suggest a superior method if possible.In problem(a)(b) (c) (d) (e) (f) (g) (h)
Give the major products of each of the following reactions. Aqueous work-up steps (when necessary) have been omitted.(a)(b) (c) (d) (e) (f)
What is the direction of the following equilibrium? H- + H2O ⇋ H2 + HO-
Formulate the product of each of the following reactions. The solvent in each case is (CH3CH2)2O.(a)(b) (c)
Write out a mechanism for every reaction depicted in Problem 38.(a)(b) (c)
Give the major products of each of the following reactions [after work-up with aqueous acid in (d), (f), and (h)].(a)(b) (c) (d) (e) (f) (g) (h)
The common practice of washing laboratory glassware with acetone can lead to unintended consequences. For example, a student plans to carry out the preparation of methylmagnesium iodide, CH3MgI,
Which of the following halogenated compounds can be used successfully to prepare a Grignard reagent for alcohol synthesis by subsequent reaction with an aldehyde or ketone? Which ones cannot and
Give the major products of each of the following reactions (after aqueous work-up). The solvent in each case is ethoxyethane (diethyl ether).(a)(b) (c) (d) (e)
For each reaction presented in Problem 43. write out the complete, step-by-step mechanism using curved-arrow notation. Include the aqueous acid work-up.(a)(b) (c) (d) (e)
Write the structures of the products of reaction of ethylmagnesium bromide, CH3CH2MgBr, with each of the following carbonyl compounds. Identify any reaction that gives more than one stereoisomeric
Give the expected major product of each of the following reactions. PCC is the abbreviation for pyridinium chlorochromate (Section 8-6).(a)(b) (c) (d) (e)
Write out a mechanism for every reaction depicted in Problem 46.(a)(b) (c) (d) (e)
Give the expected major product of each of the following reaction sequences. PCC refers to pyridinium chlorochromate.(a)(b) (c)
Unlike Grignard and organolithium reagents, organometallic compounds of the most electropositive metals (Na, K, etc.) react rapidly with haloalkanes. As a result, attempts to convert RX into RNa or
The reaction of two equivalents of Mg with 1, 4-dibromobutane produces compound A. The reaction of A with two equivalents of CH3CHO (acetaldehyde). followed by work-up with dilu aqueous acid,
Suggest the best synthetic route to each of the following simple alcohols, using in each case simple alkane as your initial starting molecule. What are sonic disadvantages of beginning sy theses with
For each alcohol in Problem 51, suggest (if possible) a synthetic route that starts with, first, aldehyde and, second, a ketone.In Problem 51(a) Methanol(b) Ethanol(c) 1-Propanol(d) 2-Propanol(e)
Outline the best method for preparing each of the following compounds from an appropriate alcohol.(a)(b) CH3CH2CH2CH2COOH (c) (d) (e)
Suggest three different syntheses of 2-methyl-2-hexanol. Each route should utilize one of the following starting materials. Then use any number of steps and any other reagents needed.(a)(b) (c)
Devise three different syntheses of 3-octanol starting with (a) A ketone; (b) An aldehyde; (c) An aldehyde different from that employed in (b).
Fill in the missing reagent(s) needed to convert each molecule into the next one pictured in the synthetic scheme below. If a transformation requires more than one step, number the reagents for the
Waxes are naturally occurring esters (alkyl alkanoates) containing long, straight alkyl chains. Whale oil contains the wax 1-hexadecyl hexadecanoate, as shown in the margin. How would you synthesize
The reduced form of the coenzyme nicotinamide adenine dinucleotide (NAD+, Chemical Highlight 8-1) is abbreviated NADH. In the presence of a variety of enzyme catalysts, it acts as a biological
Reductions by NADH (Problem 58) are stereospecific, with the stereochemistry of the product controlled by an enzyme (see Chemical Highlight 8-1). The common forms of lactate and malate dehydrogenases
Chemically modified steroids have become increasingly important in medicine. Give the possible product(s) of the following reactions. In each case, identify the major stereoisomer formed on the basis
Why do the two reactions shown in Problem 60 both require the use of excess CH3MgI and CH3Li, respectively? How many equivalents of the organometallic reagents arc needed in each case? What are the
Your team has been asked to devise a synthesis of the tertiary alcohol 2-cyclohexyl-2-butanol, A. Your laboratory is well stocked with the usual organic and inorganic reagents and solvents. An
A compound known to contain only C, H, and O gives the following upon microanalysis (atomic weights: C = 12.0, H = 1.00, O = 16.0): 52.1% C, 13.1% H. It is found to have a boiling point of 78°C. Its
The compound whose structure isis best named (IUPAC): (a) 2-methyl-4-hexanol (b) 5-methyl-3-hexanol (c) l,4,4-trimethyl-2-butanol (d) l-isopropyl-2-hexanol
In this transformation, what is the best structure for "A"?(a) (b) (c) (d)
Ester hydrolysis is best illustrated by(a)(b) (c) (d)
On which side of the equation do you expect each of the following equilibria to lie (left or right)?(a) (CH3)3 COH + K-OH- (CH3)3 CO-K+ + H2O.(b) CH3OH + NH3 CH3O- + NH-4;
Give the expected major product of each of the following reactions.(a)(b) (c) (d)
For each reaction in Problem 29, write out a detailed step-by-step mechanism?
For each of the following alcohols, write the structure of the alkyloxonium ion produced after pro-tonation by strong acid; if the alkyloxonium ion is capable of losing water readily, write the
Primary alcohols are often converted into bromides by reaction with NaBr in H2SO4. Explain how this transformation works and why it might be considered a superior method to that using concentrated
Name each of the following molecules according to IUPAC.(a) (CH3)2 CHOCH2CH3(b) CH3OCH2CH2OH(c)(d) (CICH2CH2)2O (e) (f) (g) CH3OCH2CI
Explain why the boiling points of ethers are lower than those of the isomeric alcohols. Would you expect the relative water solubilities to differ in a similar way?
Write the expected major product(s) of each of the following attempted ether syntheses,(a)(b) (c) (d) (e) (f)
(a) What would be the product of reaction of rrans-2-bromocyclooctanol (margin) with NaOH? (b) Compare the effect of entropy on the transition state of this reaction with its effect in the reactions
Give the expected major product of reaction of 2,2-dimethyloxacyclopropane with each of the following reagents? (a) Dilute H2SO4 in CH3OH (b) Na+ -OCH3 in CH3OH (c) Dilute, aqueous HBr (d)
Propose a synthesis ofBeginning with cyclohexanone, And 3-bromopropanol?
Cleavage of tertiary butyl ethers requires the use of an aqueous acid (Chapter 7, Problem 57, and Section 9-8). Why do strong bases not cleave ethers (other than oxacyclopropanes)?
Provide an IUPAC name for each of the structures pictured below.(a)(b) (c) (d) (e) (f)
For each alcohol in Problem 51 of Chapter 8,'suggest a synthetic route that starts with an oxacyclopropane (if possible)?
Give the major product(s) expected from each of the reactions shown below. Watch stereochemistry.(a)(b)
Name each of the following compounds according to IUPAC?(a)(b) (c) CH3CH2CH2SO3H (d) CF3SO2CI.
In each of the following pairs of compounds, indicate which is the stronger acid and which is the stronger base? (a) CH3SH, CH3OH; (b) HS-, HO-; (c) H3S+, H2S.
Give reasonable products for each of the following reactions.(a)(b) (c) (d) (e) (f)
Give the structures of compounds A, B, and C (with stereochemistry) from the information in the following scheme?
In an attempt to make 1-chloro-l-cyclobutylpentane, the following reaction sequence was employed. The actual product isolated, however, was not the desired molecule but an isomer of it. Suggest a
Suggest better methods for the final step in Problem 61?
In an early study of the stereochemistry of nucleophilic displacements, optically pure (R)-1-deuterio-1-pentanol was treated with 4-methylphenylsulfonyl (tosyl) chloride to make the corresponding
Compare the following methods of alkene synthesis from a general primary alcohol. State the advantages and disadvantages of each one.
Sugars, being polyhydroxylic compounds, undergo reactions characteristic of alcohols. In one of the later steps in glycolysis (the metabolism of glucose), one of the glucose metabolites with a
The formidable-looking molecule 5-methyltetrahydrofolic acid (abbreviated 5-methyl-FH4) is the product of sequences of biological reactions that convert carbon atoms from a variety of simple
The role of 5-methy 1-FH4 in biology is to serve as a donor of methyl groups to small molecules. The synthesis of the amino acid methionine from homocysteine is perhaps the best-known example.For
Epinephrine (adrenalin; see also Chapter 6 Opening) is produced in your body in a two-step process that accomplishes the transfer of a methyl group from methionine (Problem 70) to norepinephrine (see
(a) Only the trans isomer of 2-bromocyclohexanol can react with sodium hydroxide to form an oxacyclopropane-containing product. Explain the lack of reactivity of the cis-isomer.(b) The synthesis of
Freshly cut garlic contains allicin, a compound responsible for the true garlic odor (see Chemical Highlight 9-4). Propose a short synthesis of allicin, starting with 3-chloropropene?
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