?Alkynes undergo hydroboration to give alkenylboranes, which can be oxidized to give

Write structural formulas and give the IUPAC names for all the alkynes of molecular formula C5H8.

How do bond distances and bond strengths change with electronegativity in the series NH3, H2O, and HF?

Complete each of the following equations to show the conjugate acid and the conjugate base formed by proton transfer between the indicated species. Use curved arrows to show the flow of electrons, and specify whether the position of equilibrium lies to the side of reactants or products.

Which of the alkynes of molecular formula C5H8 can be prepared in good yield by alkylation or dialkylation of acetylene? Explain why the preparation of the other C5H8 isomers would not be practical.

A certain hydrocarbon had the molecular formula C16H26 and contained two triple bonds. Ozonolysis gave CH3(CH2)4CO2H and HO2CCH2CH2CO2H as the only products. Suggest a reasonable structure for this hydrocarbon.

Outline a synthesis of (E)-H2C CHCH2CH2CH CHCH3 from propyne, organic compounds with four carbons or fewer, and any necessary inorganic reagents.

Provide the IUPAC name for each of the following alkynes: (a) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{C} \equiv \mathrm{CH}\) (b) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{C} \equiv \mathrm{CCH}_{3}\) Text Transcription: CH_3CH_2CH_2C equiv CH CH_3CH_2C equiv CCH_3

Oropheic acid is the common name of a naturally occurring acetylenic carboxylic acid having the molecular formula C18H22O2. Its systematic name is 17-octadecene-9,11,13- triynoic acid. What is its structural formula?

Write structural formulas for all the alkynes of molecular formula C8H14 that yield 3-ethylhexane on catalytic hydrogenation.

An unknown acetylenic amino acid obtained from the seed of a tropical fruit has the molecular formula C7H11NO2. On catalytic hydrogenation over platinum, this amino acid yielded homoleucine (an amino acid of known structure shown here) as the only product. What is the structure of the unknown amino acid?

Oleic acid and stearic acid are naturally occurring compounds, which can be isolated from various fats and oils. In the laboratory, each can be prepared by hydrogenation of a compound known as stearolic acid, which has the formula CH3(CH2)7C C(CH2)7CO2H. Oleic acid is obtained by hydrogenation of stearolic acid over Lindlar palladium; stearic acid is obtained by hydrogenation over platinum. What are the structures of oleic acid and stearic acid?

When 2-heptyne was treated with aqueous sulfuric acid containing mercury(II) sulfate, two products, each having the molecular formula C7H14O, were obtained in approximately equal amounts. What are these two compounds?

All the following reactions have been described in the chemical literature and proceed in good yield. In some cases the reactants are more complicated than those we have so far encountered. Nevertheless, on the basis of what you have already learned, you should be able to predict the principal product in each case.

Compound A has the molecular formula C14H25Br and was obtained by reaction of sodium acetylide with 1,12-dibromododecane. On treatment of compound A with sodium amide, it was converted to compound B (C14H24). Ozonolysis of compound B gave the diacid HO2C(CH2)12CO2H. Catalytic hydrogenation of compound B over Lindlar palladium gave compound C (C14H26), and hydrogenation over platinum gave compound D (C14H28). C yielded O=CH(CH2)12CH=O on ozonolysis. Assign structures to compounds A through D so as to be consistent with the observed transformations.

When 1,2-dibromodecane was treated with potassium hydroxide in aqueous ethanol, it yielded a mixture of three isomeric compounds of molecular formula C10H19Br. Each of these compounds was converted to 1-decyne on reaction with sodium amide in dimethyl sulfoxide. Identify these three compounds.

Diphenylacetylene can be synthesized by the double dehydrohalogenation of 1,2-dibromo- 1,2-diphenylethene. The sequence starting from (E)-1,2-diphenylethene consists of bromination to give the dibromide, followed by dehydrohalogenation to give a vinylic bromide, then a second dehydrohalogenation to give diphenylacetylene. (a) What is the structure, including stereochemistry, of the vinylic bromide? (b) If the sequence starts with (Z)-1,2-dibromo-1,2-diphenylethene, what is (are) the structure(s) of the intermediate dibromide(s)? What is the structure of the vinylic bromide?

(Z)-9-Tricosene [(Z)-CH3(CH2)7CH CH(CH2)12CH3] is the sex pheromone of the female housefly. Synthetic (Z)-9-tricosene is used as bait to lure male flies to traps that contain insecticide. Using acetylene and alcohols of your choice as starting materials, along with any necessary inorganic reagents, show how you could prepare (Z)-9-tricosene.

The ketone 2-heptanone has been identified as contributing to the odor of a number of dairy products, including condensed milk and cheddar cheese. Describe a synthesis of 2-heptanone from acetylene and any necessary organic or inorganic reagents.

Show by writing a suitable series of equations how you could prepare each of the following compounds from the designated starting materials and any necessary organic or inorganic reagents: (a) 2,2-Dibromopropane from 1,1-dibromopropane (b) 2,2-Dibromopropane from 1,2-dibromopropane (c) 1,1,2,2-Tetrachloropropane from 1,2-dichloropropane (d) 2,2-Diiodobutane from acetylene and ethyl bromide (e) 1-Hexene from 1-butene and acetylene (f) Decane from 1-butene and acetylene (g) Cyclopentadecyne from cyclopentadecene

Alkynes undergo hydroboration to give alkenylboranes, which can be oxidized to give carbonyl compounds with hydrogen peroxide. The net result of the two-step sequence is hydration, which gives aldehydes from terminal alkynes. The oxidation step involves an enol intermediate. Using Mechanism 9.1 as a guide, write the structure of the enol that is formed in the conversion of 1-hexyne to hexanal.

The preparation and properties of alkynes extend some topics explored in earlier chapters: Alkynes can be prepared by elimination reactions related to the E2 dehydrohalogenation of alkyl halides used to prepare alkenes. Alkynes can be prepared by SN2 reactions in which a nucleophile of the type \(\mathrm{RC} \equiv \mathrm{C}:^{-}\) reacts with a primary alkyl halide. Alkynes undergo addition reactions, especially electrophilic addition, with many of the same compounds that add to alkenes. The greater s character of sp hybrid orbitals compared with sp3 and sp2 gives alkynes certain properties beyond those seen in alkanes and alkenes. It is convenient to think of sp-hybridized carbon as more electronegative than its sp2 or sp3 counterparts. The \(\equiv \mathrm{C}-\mathrm{H}\) unit of an alkyne is more acidic than a C?H unit of an alkene or alkane, allowing acetylene and terminal alkynes to be converted to their conjugate bases \(\equiv \mathrm{C}^{-}\) by NaNH2. Unlike alkenes, alkynes are reduced by metals, especially Li, Na, and K. Unlike alkenes, alkynes can undergo nucleophilic as well as electrophilic addition. Problems 9.38–9.42 emphasize mechanistic reasoning. By thinking mechanistically you reduce the need to memorize facts while increasing your ability to analyze and understand new material. Nucleophilic addition to alkynes, for example, is not covered in this chapter but is the focus of Problem 9.42, which can be solved by thinking mechanistically. Which of the following best describes what happens in the first step in the mechanism of the reaction shown? Text Transcription: RC equiv C:^- equiv C-H equiv C^-

The preparation and properties of alkynes extend some topics explored in earlier chapters: Alkynes can be prepared by elimination reactions related to the E2 dehydrohalogenation of alkyl halides used to prepare alkenes. Alkynes can be prepared by SN2 reactions in which a nucleophile of the type \(\mathrm{RC} \equiv \mathrm{C}:^{-}\) reacts with a primary alkyl halide. Alkynes undergo addition reactions, especially electrophilic addition, with many of the same compounds that add to alkenes. The greater s character of sp hybrid orbitals compared with sp3 and sp2 gives alkynes certain properties beyond those seen in alkanes and alkenes. It is convenient to think of sp-hybridized carbon as more electronegative than its sp2 or sp3 counterparts. The \(\equiv \mathrm{C}-\mathrm{H}\) unit of an alkyne is more acidic than a C?H unit of an alkene or alkane, allowing acetylene and terminal alkynes to be converted to their conjugate bases \(\equiv \mathrm{C}^{-}\) by NaNH2. Unlike alkenes, alkynes are reduced by metals, especially Li, Na, and K. Unlike alkenes, alkynes can undergo nucleophilic as well as electrophilic addition. Problems 9.38–9.42 emphasize mechanistic reasoning. By thinking mechanistically you reduce the need to memorize facts while increasing your ability to analyze and understand new material. Nucleophilic addition to alkynes, for example, is not covered in this chapter but is the focus of Problem 9.42, which can be solved by thinking mechanistically. Which of the following best describes what happens in the first step in the mechanism of the hydrogen–deuterium exchange reaction shown? Text Transcription: RC equiv C:^- equiv C-H equiv C^-

The preparation and properties of alkynes extend some topics explored in earlier chapters: Alkynes can be prepared by elimination reactions related to the E2 dehydrohalogenation of alkyl halides used to prepare alkenes. Alkynes can be prepared by SN2 reactions in which a nucleophile of the type \(\mathrm{RC} \equiv \mathrm{C}:^{-}\) reacts with a primary alkyl halide. Alkynes undergo addition reactions, especially electrophilic addition, with many of the same compounds that add to alkenes. The greater s character of sp hybrid orbitals compared with sp3 and sp2 gives alkynes certain properties beyond those seen in alkanes and alkenes. It is convenient to think of sp-hybridized carbon as more electronegative than its sp2 or sp3 counterparts. The \(\equiv \mathrm{C}-\mathrm{H}\) unit of an alkyne is more acidic than a C?H unit of an alkene or alkane, allowing acetylene and terminal alkynes to be converted to their conjugate bases \(\equiv \mathrm{C}^{-}\) by NaNH2. Unlike alkenes, alkynes are reduced by metals, especially Li, Na, and K. Unlike alkenes, alkynes can undergo nucleophilic as well as electrophilic addition. Problems 9.38–9.42 emphasize mechanistic reasoning. By thinking mechanistically you reduce the need to memorize facts while increasing your ability to analyze and understand new material. Nucleophilic addition to alkynes, for example, is not covered in this chapter but is the focus of Problem 9.42, which can be solved by thinking mechanistically. Electrophilic addition of fluorosulfonic acid (FSO2OH) to propyne proceeds by way of a very unstable vinyl cation intermediate. What is the most reasonable structure, including geometry, of this intermediate? (Hint: Use VSEPR to deduce the geometry.) Text Transcription: RC equiv C:^- equiv C-H equiv C^-

The preparation and properties of alkynes extend some topics explored in earlier chapters: Alkynes can be prepared by elimination reactions related to the E2 dehydrohalogenation of alkyl halides used to prepare alkenes. Alkynes can be prepared by SN2 reactions in which a nucleophile of the type \(\mathrm{RC} \equiv \mathrm{C}:^{-}\) reacts with a primary alkyl halide. Alkynes undergo addition reactions, especially electrophilic addition, with many of the same compounds that add to alkenes. The greater s character of sp hybrid orbitals compared with sp3 and sp2 gives alkynes certain properties beyond those seen in alkanes and alkenes. It is convenient to think of sp-hybridized carbon as more electronegative than its sp2 or sp3 counterparts. The \(\equiv \mathrm{C}-\mathrm{H}\) unit of an alkyne is more acidic than a C?H unit of an alkene or alkane, allowing acetylene and terminal alkynes to be converted to their conjugate bases \(\equiv \mathrm{C}^{-}\) by NaNH2. Unlike alkenes, alkynes are reduced by metals, especially Li, Na, and K. Unlike alkenes, alkynes can undergo nucleophilic as well as electrophilic addition. Problems 9.38–9.42 emphasize mechanistic reasoning. By thinking mechanistically you reduce the need to memorize facts while increasing your ability to analyze and understand new material. Nucleophilic addition to alkynes, for example, is not covered in this chapter but is the focus of Problem 9.42, which can be solved by thinking mechanistically. Rates of Br2 addition were measured for a series of alkynes, giving the data shown. Assuming that Br2 addition to alkynes proceeds through rate-determining formation of a cyclic bromonium ion, what generalizations can you make about the structure of the rate- determining transition state? Text Transcription: RC equiv C:^- equiv C-H equiv C^-

The preparation and properties of alkynes extend some topics explored in earlier chapters: Alkynes can be prepared by elimination reactions related to the E2 dehydrohalogenation of alkyl halides used to prepare alkenes. Alkynes can be prepared by SN2 reactions in which a nucleophile of the type \(\mathrm{RC} \equiv \mathrm{C}:^{-}\) reacts with a primary alkyl halide. Alkynes undergo addition reactions, especially electrophilic addition, with many of the same compounds that add to alkenes. The greater s character of sp hybrid orbitals compared with sp3 and sp2 gives alkynes certain properties beyond those seen in alkanes and alkenes. It is convenient to think of sp-hybridized carbon as more electronegative than its sp2 or sp3 counterparts. The \(\equiv \mathrm{C}-\mathrm{H}\) unit of an alkyne is more acidic than a C?H unit of an alkene or alkane, allowing acetylene and terminal alkynes to be converted to their conjugate bases \(\equiv \mathrm{C}^{-}\) by NaNH2. Unlike alkenes, alkynes are reduced by metals, especially Li, Na, and K. Unlike alkenes, alkynes can undergo nucleophilic as well as electrophilic addition. Problems 9.38–9.42 emphasize mechanistic reasoning. By thinking mechanistically you reduce the need to memorize facts while increasing your ability to analyze and understand new material. Nucleophilic addition to alkynes, for example, is not covered in this chapter but is the focus of Problem 9.42, which can be solved by thinking mechanistically. Nucleophilic addition can occur with alkynes that bear strong electron-attracting substituents such as CF3 on the triple bond. Predict the product of nucleophilic addition of CH3OD to 3,3,3-trifluoropropyne. The stereochemistry of addition is anti, and the first step in the mechanism is bond formation between CH3O? and one of the carbons of the triple bond. Text Transcription: RC equiv C:^- equiv C-H equiv C^-

Use curved arrows to show how calcium carbide reacts with water to give acetylene.

Outline efficient syntheses of each of the following alkynes from acetylene and any necessary organic or inorganic reagents: (a) 1-Heptyne (b) 2-Heptyne (c) 3-Heptyne

Give the structures of three isomeric dibromides that could be used as starting materials for the preparation of 3,3-dimethyl-1-butyne.

Show, by writing an appropriate series of equations, how you could prepare propyne from each of the following compounds as starting materials. You may use any necessary organic or inorganic reagents. (a) 2-Propanol (b) 1-Propanol (c) Isopropyl bromide (d) 1,1-Dichloroethane (e) Ethyl alcohol

Write a series of equations showing how you could prepare octane from acetylene and any necessary organic and inorganic reagents.

Write a series of equations showing how to prepare cis-5-decene from acetylene and 1–bromobutane as the source of all its carbons, using any necessary organic or inorganic reagents. (Hint: You may find it helpful to review Section 9.6.)

Design a synthesis of 1,1-dichloroethane from each of the following. (a) Ethylene (b) Vinyl chloride (H2C=CHCl) (c) 1,1-Dibromoethane

Give the structure of the enol formed by hydration of 2-butyne, and write a series of equations showing its conversion to its corresponding ketone isomer.

Show by a series of equations how you could prepare 2-octanone from acetylene and any necessary organic or inorganic reagents. How could you prepare 4-octanone?

Write a structural formula for each of the following: (a) 1-Octyne (b) 2-Octyne (c) 3-Octyne (d) 4-Octyne (e) 2,5-Dimethyl-3-hexyne (f) 4-Ethyl-1-hexyne (g) Ethynylcyclohexane (h) 3-Ethyl-3-methyl-1-pentyne

All compounds in Problem 9.17 are isomers except one. Which one?

The alkane formed by hydrogenation of (S)-4-methyl-1-hexyne is optically active, but the one formed by hydrogenation of (S)-3-methyl-1-pentyne is not. Explain. Would you expect the products of hydrogenation of these two compounds in the presence of Lindlar palladium to be optically active?

Write the structure of the major organic product isolated from the reaction of 1-hexyne with (a) Hydrogen (2 mol), platinum (b) Hydrogen (1 mol), Lindlar palladium (c) Sodium amide in liquid ammonia (d) Product in part (c) treated with 1-bromobutane (e) Product in part (c) treated with tert-butyl bromide (f) Hydrogen chloride (1 mol) (g) Hydrogen chloride (2 mol) (h) Chlorine (1 mol) (i) Chlorine (2 mol) (j) Aqueous sulfuric acid, mercury(II) sulfate (k) Ozone followed by hydrolysis

Write the structure of the major organic product isolated from the reaction of 3-hexyne with (a) Hydrogen (2 mol), platinum (b) Hydrogen (1 mol), Lindlar palladium (c) Hydrogen chloride (1 mol) (d) Hydrogen chloride (2 mol) (e) Chlorine (1 mol) (f) Chlorine (2 mol) (g) Aqueous sulfuric acid, mercury(II) sulfate (h) Ozone followed by hydrolysis

Show by writing appropriate chemical equations how each of the following compounds could be converted to 1-hexyne: (a) 1,1-Dichlorohexane (b) 1-Hexene (c) Acetylene (d) 1-Iodohexane

Show by writing appropriate chemical equations how each of the following compounds could be converted to 3-hexyne: (a) 1-Butene (b) 1,1-Dichlorobutane (c) Acetylene

Assume that you need to prepare 4-methyl-2-pentyne and discover that the only alkynes on hand are acetylene and propyne. You also have available methyl iodide, isopropyl bromide, and 1,1-dichloro-3-methylbutane. Which of these compounds would you choose in order to perform your synthesis, and how would you carry it out?