Solved: Some of the following examples can show geometric isomerism, and some cannot

(a) If a hydrocarbon has nine carbon atoms, three double bonds, and one ring, how many hydrogen atoms must it have? (b) Calculate the number of elements of unsaturation implied by the molecular formula (c) Give five examples of structures with this formula At least one should contain a ring, and at least one a double bond.

Draw five more compounds of formula C4H6NOCl.

Draw five more compounds of formula C4H6NOCl.

For each of the following molecular formulas, determine the number of elements of unsaturation, and draw three examples. (a) (b) (c) (d) (e) C C6H3NClBr

Give the systematic (IUPAC) names of the following alkenes. (a) (b) (c) (d) CH2CHCH2CHCH2 CH2CCHCHCH2

1. Determine which of the following compounds show cis-trans isomerism. 2. Draw and name the cis and trans (or Z and E) isomers of those that do.

The following names are all incorrect. Draw the structure represented by the incorrect name (or a consistent structure if the name is ambiguous), and give your drawing the correct name. (a) cis-2,3-dimethyl-2-pentene (b) 3-vinylhex-4-ene (c) 2-methylcyclopentene (d) 6-chlorocyclohexadiene (e) 2,5-dimethylcyclohexene (f) cis-2,5-dibromo-3-ethylpent-2-ene

Some of the following examples can show geometric isomerism, and some cannot. For the ones that can, draw all the geometric isomers, and assign complete names using the E-Z system. (a) 3-bromo-2-chloropent-2-ene (b) 3-ethylhexa-2,4-diene (c) 3-bromo-2-methylhex-3-ene (d) penta-1,3-diene (e) 3-ethyl-5-methyloct-3-ene (f) 3,7-dichloroocta-2,5-diene

Use the data in Table 7-1 to predict the energy difference between 2,3-dimethyl-but-1-ene and 2,3-dimethylbut-2-ene. Which of these double-bond isomers is more stable?

Using Table 7-1 as a guide, predict which member of each pair is more stable, and by about how many kJ mol or kcal mol. (a) cis,cis-hexa-2,4-diene or trans,trans-hexa-2,4-diene (b) 2-methylbut-1-ene or 3-methylbut-1-ene (c) 2-methylbut-1-ene or 2-methylbut-2-ene (d) 2,3-dimethylbut-1-ene or 2,3-dimethylbut-2-ene

Explain why each of the following alkenes is stable or unstable. (a) 1,2-dimethylcyclopentene (b) trans-1,2-dimethylcyclopentene (c) trans-3,4-dimethylcyclopentene (d) trans-1,2-dimethylcyclodecene

For each pair of compounds, predict the one with a higher boiling point. Which compounds have zero dipole moments? (a) cis-1,2-dichloroethene or cis-1,2-dibromoethene (b) cis- or trans-2,3-dichlorobut-2-ene (c) cyclohexene or 1,2-dichlorocyclohexene

For each reaction, decide whether substitution or elimination (or both) is possible, and predict the products you expect. Label the major products. (a) (b) (c) in (d) chlorocyclohexane + NaOC1CH323 in 1CH323COH

Show that the (S,S) enantiomer of this (R,R) diastereomer of 1-bromo-1,2-diphenylpropane also undergoes E2 elimination to give the cis diastereomer of the product. (We do not expect these achiral reagents to distinguish between enantiomers.)

Show that the (S,S) enantiomer of this (R,R) diastereomer of 1-bromo-1,2-diphenylpropane also undergoes E2 elimination to give the cis diastereomer of the product. (We do not expect these achiral reagents to distinguish between enantiomers.)

Predict the elimination products of the following reactions, and label the major products. (a) cis-1-bromo-2-methylcyclohexane in (b) trans-1-bromo-2-methylcyclohexane in CH + NaOCH3 3OH

When the following stereoisomer of 2-bromo-1,3-dimethylcyclohexane is treated with sodium methoxide, no E2 reaction is observed. Explain why this compound cannot undergo the E2 reaction in the chair conformation.

(a) Two stereoisomers of a bromodecalin are shown. Although the difference between these stereoisomers may seem trivial, one isomer undergoes elimination with KOH much faster than the other. Predict the products of these eliminations, and explain the large difference in the ease of elimination.

Give the expected product(s) of E2 elimination for each reaction. (Hint: Use models!)

Give the expected product(s) of E2 elimination for each reaction. (Hint: Use models!)

Give the expected product(s) of E2 elimination for each reaction. (Hint: Use models!)

Predict the elimination products formed by debromination of the following compounds with iodide ion in acetone. Include stereochemistry, and give a correct name for each product. (a) trans-1,2-dibromocyclohexane (b) (3R,4R)-3,4-dibromoheptane

Predict the elimination products formed by debromination of the following compounds with iodide ion in acetone. Include stereochemistry, and give a correct name for each product. (a) trans-1,2-dibromocyclohexane (b) (3R,4R)-3,4-dibromoheptane

Propose mechanisms for the following reactions.

Propose mechanisms for the following reactions

The dehydrogenation of butane to trans-but-2-ene has and (a) Compute the value of for dehydrogenation at room temperature (25 C or 298 K). Is dehydrogenation favored or disfavored? (b) Compute the value of for dehydrogenation at 1000 C, assuming and are constant. Is dehydrogenation favored or disfavored?

For practice in recognizing mechanisms, classify each reaction according to the type of mechanism you expect: 1. Free-radical chain reaction 2. Reaction involving strong bases and strong nucleophiles 3. Reaction involving strong acids and strong electrophiles

Propose mechanisms for the following reactions. Additional products may be formed, but your mechanism only needs to explain the products shown.

Propose mechanisms for the following reactions.

Using cyclohexane as your starting material, show how you would synthesize each of the following compounds. (Once you have shown how to synthesize a compound, you may use it as the starting material in any later parts of this problem.)

Using cyclohexane as your starting material, show how you would synthesize each of the following compounds. (Once you have shown how to synthesize a compound, you may use it as the starting material in any later parts of this problem.)

Give a correct name for each compound.

Label each structure as Z, E, or neither.

a) Draw and name all five isomers of formula (b) Draw all 12 acyclic (no rings) isomers of formula Include stereoisomers. (c) Cholesterol, has only one pi bond. With no additional information, what else can you say about its structure?

Draw and name all stereoisomers of 3-chlorohepta-2,4-diene (a) Using the cis-trans nomenclature. (b) Using the E-Z nomenclature.

Determine which compounds show cis-trans isomerism. Draw and label the isomers, using both the cis-trans and E-Z nomenclatures where applicable. (a) pent-1-ene (b) pent-2-ene (c) hex-3-ene (d) 1,1-dibromopropene (e) 1,2-dibromopropene (f) 1-bromo-1-chlorohexa-1,3-diene

For each alkene, indicate the direction of the dipole moment. For each pair, determine which compound has the larger dipole moment. (a) cis-1,2-difluoroethene or trans-1,2-difluoroethene (b) cis-1,2-dibromoethene or trans-2,3-dibromobut-2-ene (c) cis-1,2-dibromo-1,2-dichloroethene or cis-1,2-dichloroethene

Predict the products of the following reactions. When more than one product is expected, predict which will be the major product.

Write a balanced equation for each reaction.

Show how you would prepare cyclopentene from each compound. (a) trans-1,2-dibromocyclopentane (b) cyclopentanol (c) cyclopentyl bromide (d) cyclopentane (not by dehydrogenation)

Predict the products formed by sodium hydroxide-promoted dehydrohalogenation of the following compounds. In each case, predict which will be the major product. (a) 1-bromobutane (b) 2-chlorobutane (c) 3-bromopentane (d) cis-1-bromo-2-methylcyclohexane (e) trans-1-bromo-2-methylcyclohexane

What halides would undergo dehydrohalogenation to give the following pure alkenes? (a) hex-1-ene (b) isobutylene (c) pent-2-ene (d) methylenecyclohexane (e) 4-methylcyclohexene

In the dehydrohalogenation of alkyl halides, a strong base such as tert-butoxide usually gives the best results via the E2 mechanism. (a) Explain why a strong base such as tert-butoxide cannot dehydrate an alcohol through the E2 mechanism. (b) Explain why strong acid, used in the dehydration of an alcohol, is not effective in the dehydrohalogenation of an alkyl halide

Predict the major products of acid-catalyzed dehydration of the following alcohols. (a) pentan-2-ol (b) 1-methylcyclopentanol (c) 2-methylcyclohexanol (d) 2,2-dimethylpropan-1-ol

Propose mechanisms for the following reactions. Additional products may be formed, but your mechanism only needs to explain the products shown.

Predict the dehydrohalogenation product(s) that result when the following alkyl halides are heated in alcoholic KOH. When more than one product is formed, predict the major and minor products

E1 eliminations of alkyl halides are rarely useful for synthetic purposes because they give mixtures of substitution and elimination products. Explain why the sulfuric acid-catalyzed dehydration of cyclohexanol gives a good yield of cyclohexene even though the reaction goes by an E1 mechanism. (Hint: What are the nucleophiles in the reaction mixture? What products are formed if these nucleophiles attack the carbocation? What further reactions can these substitution products undergo?)

The following reaction is called the pinacol rearrangement. The reaction begins with an acid-promoted ionization to give a carbocation. This carbocation undergoes a methyl shift to give a more stable, resonance-stabilized cation. Loss of a proton gives the observed product. Propose a mechanism for the pinacol rearrangement

Propose a mechanism to explain the formation of two products in the following reaction.

A chemist allows some pure (2S,3R)-3-bromo-2,3-diphenylpentane to react with a solution of sodium ethoxide in ethanol. The products are two alkenes: A (cis-trans mixture) and B, a single pure isomer. Under the same conditions, the reaction of (2S,3S)-3-bromo-2,3-diphenylpentane gives two alkenes, A (cis-trans mixture) and C. Upon catalytic hydrogenation, all three of these alkenes (A, B, and C) give 2,3-diphenylpentane. Determine the structures of A, B, and C, give equations for their formation, and explain the stereospecificity of these reactions

A chemist allows some pure (2S,3R)-3-bromo-2,3-diphenylpentane to react with a solution of sodium ethoxide in ethanol. The products are two alkenes: A (cis-trans mixture) and B, a single pure isomer. Under the same conditions, the reaction of (2S,3S)-3-bromo-2,3-diphenylpentane gives two alkenes, A (cis-trans mixture) and C. Upon catalytic hydrogenation, all three of these alkenes (A, B, and C) give 2,3-diphenylpentane. Determine the structures of A, B, and C, give equations for their formation, and explain the stereospecificity of these reactions

A double bond in a six-membered ring is usually more stable in an endocyclic position than in an exocyclic position. Hydrogenation data on two pairs of compounds follow. One pair suggests that the energy difference between endocyclic and exocyclic double bonds is about 9 kJ mol. The other pair suggests an energy difference of about 5 kJ mol. Which number do you trust as being more representative of the actual energy difference? Explain your answer.

Predict the products of the following eliminations of vicinal dibromides with potassium iodide. Remember to consider the geometric constraints of the E2 reaction.

One of the following dichloronorbornanes undergoes elimination much faster than the other. Determine which one reacts faster, and explain the large difference in rates.

A graduate student wanted to make methylenecyclobutane, and he tried the following reaction. Propose structures for the other products, and give mechanisms to account for their formation.

Write a mechanism that explains the formation of the following product. In your mechanism, explain the cause of the rearrangement, and explain the failure to form the Zaitsev product.

hen 2-bromo-3-phenylbutane is treated with sodium methoxide, two alkenes result (by E2 elimination). The Zaitsev product predominates. (a) Draw the reaction, showing the major and minor products. (b) When one pure stereoisomer of 2-bromo-3-phenylbutane reacts, one pure stereoisomer of the major product results. For example, when (2R,3R)-2-bromo-3-phenylbutane reacts, the product is the stereoisomer with the methyl groups cis. Use your models to draw a Newman projection of the transition state to show why this stereospecificity is observed. (c) Use a Newman projection of the transition state to predict the major product of elimination of (2S,3R)-2-bromo-3- phenylbutane. (d) Predict the major product from elimination of (2S,3S)-2-bromo-3-phenylbutane. This prediction can be made without drawing any structures, by considering the results in part (b).

A student adds NBS to a solution of 1-methylcyclohexene and irradiates the mixture with a sunlamp until all the NBS has reacted. After a careful distillation, the product mixture contains two major products of formula C7H11Br. (a) Draw the resonance forms of the three possible allylic free radical intermediates. (b) Rank these three intermediates from least stable to most stable. (c) Draw the products obtained from each free-radical intermediate. (d) The two major products are the ones with the most stable double bonds that result from the two most stable intermediates. Indicate the compounds that are likely to be the major products

Explain the dramatic difference in rotational energy barriers of the following three alkenes. (Hint: Consider what the transition states must look like.) * * Ph Ph 259 kJ/mol