chapter 7

Organic Chemistry, 8e (Bruice) Chapter 7 The Reactions of Alkynes - Introduction to Multistep Synthesis What is the IUPAC name for the following alkyne? 4671588241305-Bromo-2-heptyne 3-Bromo-5-heptyne 2-Bromo-2-methyl-4-hexyne 5-Bromo-5,5-dimethylhexyne 5-Bromo-5-methyl-2-hexyne Answer: E Section: 7-1 How many distinct terminal alkynes exist with a molecular formula of C5H8? 1 2 3 4 5 Answer: B Section: 7-1 How many distinct internal alkynes exist with a molecular formula of C6H10? 1 2 3 4 5 Answer: C Section: 7-1 What is the common name for the following alkyne? 557656495150neohexyne trimethylpropyne trimethylacetylene tert-butylacetylene isopropylacetylene Answer: D Section: 7-1 9594854171950Write structures and give IUPAC names for all alkynes with molecular formula C5H8. Answer: Section: 7-1 Give the IUPAC name for (CH3)2C(CH2CH3)CCCH(CH3)2. Answer: 2,5,5-trimethyl-3-heptyne Section: 7-1 Give the IUPAC name for HCCCH2CH2CH3. Answer: 1-pentyne Section: 7-1 Give the IUPAC name for BrCH2CH2CCCH2CH3. Answer: 1-bromo-3-hexyne Section: 7-1 Draw an acceptable structure for acetylene. Answer: C–H Section: 7-1 Draw an acceptable structure for 3-sec-butyl-1-heptyne. Answer: Section: 7-1 Draw an acceptable structure for 2-hexyne. Answer: Section: 7-1 Provide the systematic name of the compound shown. Answer: 5,6,6-trimethyl-1-heptyne Section: 7-1 Give the systematic name for the alkyne Cl3CCH2CH2CCCH3. Answer: 6,6,6-trichloro-2-hexyne Section: 7-1 Provide the structure of all distinct terminal alkynes with a molecular formula of C6H10. Answer: Section: 7-1 269265120609700Name the following compound. 3-heptyn-6-ol 3-hepten-6-ol 4-hepten-2-ol 4-heptyn-2-ol 4-heptan-2-ol Answer: D Section: 7-2 Name the following compound. Answer: cis-4,5-dimethyl-4-hepten-2-yne or (Z)-4,5-dimethyl-4-hepten-2-yne Section: 7-2 914400223813Provide an acceptable name for the compound shown. Answer: 7,7-dichloro-5,5-dimethyl-3-heptyne or 7,7-dichloro-5,5-dimethylhept-3-yne Section: 7-1 Give the IUPAC name for the following compound. 400163117568800isoprene 3-methyl-1,3-butadiene 2-methyl-1,3-butadiene 2-methyl-2,3-butadiene isobutadiene Answer: C Section: 5-2 What is the IUPAC name for the following compound? 25204548926500 cis, trans-2, 4-heptadiene 2Z,4Z-2, 4-heptadiene cis, cis-2, 4-heptadiene trans, trans-2, 4-heptadiene 2E,4E-2, 4-heptadiene Answer: A Section: 5-2 937260221416Give the systematic name of the compound shown below. Answer: 1,7-dimethyl-1,3-cycloheptadiene Section: 5-2 914400235498Give the systematic name of the compound shown below. Answer: (S)-5-methyl-5-hexen-2-ol Section: 5-2 959111219741Name the following compound. Answer: (2E,4Z)-2,4-hexadiene or trans, cis-2,4-hexadiene or (2Z,4E)-2,4-hexadiene or cis, trans-2,4-hexadiene Section: 5-2 Provide the structure of (2E,4E)-2-chloro-2,4-octadiene. Answer: Section: 5-2 Provide the systematic name of the compound shown. Answer: (E)-5-methyl-5-hepten-1-yne Section: 7-2 Which of the following improperly describes the physical properties of an alkyne? relatively nonpolar nearly insoluble in water less dense than water insoluble in most organic solvents Answer: D Section: 7-4 What are the hybridizations of the carbon atoms numbered 1 and 2 respectively in the following structure? 18033996731000sp3, sp2 sp2, sp2 sp, sp sp2, sp sp, sp2 Answer: D Section: 7-3 Which of the following statements is not true about propyne, C—CH3? It contains six sigma bonds. It contains three pi bonds. The H—C—H bond angle is about 109.5°. The C—C—C bond angle is 180°. The pi bond is weaker than the sigma bond. Answer: B Section: 7-3 The carbon-carbon triple bond of an alkyne is composed of three ? bonds. two ? bonds and one ? bond. one ? bond and two ? bonds. three ? bonds. Answer: C Section: 7-3 What are the hybridizations of the carbon atoms numbered 1 and 2 in the structure below? 1 2 H3C-CHCH-CC-H sp3, sp2 sp2, sp2 sp2, sp sp, sp Answer: D Section: 7-3 What two atomic orbitals or hybrid atomic orbitals overlap to form the carbon-carbon ? bond in ethyne? sp3—sp3 p—p sp2—sp2 s—s sp—sp Answer: E Section: 7-3 Which of the following statements correctly describes the general reactivity of alkynes? An alkyne is an electron-rich molecule and therefore reacts as a nucleophile. The ? bonds of alkynes are higher in energy than the ? bonds and are thus more reactive. Unlike alkenes, alkynes fail to undergo electrophilic addition reactions. Alkynes are generally more reactive than alkenes. Alkynes react as electrophiles, whereas alkenes reacts as nucleophiles. Answer: A Section: 7-5 Although you might expect 1-propyne to be more reactive than 1-propene in electrophilic addition reactions, the reverse is true. Explain this using your knowledge of the mechanism of electrophilic additions to both alkynes and alkenes. 91440017589500Answer: When HCl is added to an alkene, a secondary carbocation intermediate is formed, When HCl is added to an alkyne, a vinylic cation is formed as an intermediate, Alkenes are more reactive than alkynes since the difference in stabilities between the carbocations is greater than the difference in stabilities between the alkene and alkyne. Section: 7-5 1303782287060What is the major product of the following reaction? CH3C 2451360309172020402857500 50651792750000481210027088 A) B) C) CH—Cl D) E) Answer: B Section: 7-6 Which of the following is the best synthesis of 2, 2-dibromopropane? 542173169500 262295010023500 Answer: C Section: 7-6 In the addition of hydrogen bromide to alkynes in the absence of peroxides, which of the following species is believed to be an intermediate? vinyl anion vinyl cation vinyl radical carbene bromonium ion Answer: B Section: 7-6 is produced when 1 equivalent of HBr is added to 1-hexyne. 2-bromo-1-hexene E-1-bromo-1-hexene Z-1-bromo-1-hexene A mixture of E and Z isomers of 1-bromo-1-hexene E-2-bromo-2-hexene Answer: A Section: 7-6 Which of the following compounds is the major product when 1-hexyne is treated with excess HBr? 1,1-dibromohexane 1,1-dibromohexene 1,2-dibromohexene 1,2-dibromohexane 2,2-dibromohexane Answer: E Section: 7-6 Provide the structure of the major organic product(s) in the reaction below. Answer: Section: 7-6 Provide the structure of the major organic product of the following reaction. Answer: Section: 7-6 Provide the structure of the major organic product of the following reaction. Answer: Section: 7-6 Provide the major organic product in the reaction below. 91440022669500Answer: Section: 7-6 Provide the major organic product in the reaction below. 91440022415500Answer: Section: 7-6 Provide the major organic product in the reaction below. 91440019939000Answer: Section: 7-6 91440022288500Provide the major organic product in the reaction below. Answer: Section: 7-6 91440018859500Provide the major organic product in the reaction below. Answer: Section: 7-9 MCAT: 9.2 Give the major organic product for the reaction. 41582565824590021488965786880021971058157800 A) B) C) 2519686114501001134198110434 D) E) Answer: D Section: 7-6 Give the major organic product for the reaction. 42015695124950021989485792900032016558149000 A) B) C) 25923971265920035343212132300 D) E) Answer: E Section: 7-6 Provide the structure of the major organic product that results when 2-butyne is treated with 1 equivalent of HCl. Answer: Section: 7-6 Provide the structure of the major organic product that results when 2-butyne is treated with 2 equivalents of HCl. Answer: CH3CH2CCl2CH3 Section: 7-6 Provide the structure of the major organic product that results when 2-butyne is treated with 1 equivalent of Br2. 950975205301Answer: Section: 7-6 959114258131Which of the following are enol forms of 2-butanone? A) 960125243861B) C) 959107228385D) E) Answer: E Section: 7-7 Which of the following is the final and major product of this reaction? 26834736477000 I II III IV V Answer: A Section: 7-7 Provide the structure of the major organic product(s) in the reaction below. Answer: Section: 7-7 960125433070For the reaction below indicate whether the equilibrium constant will be greater than 1 or less than 1. Answer: less than 1 Section: 7-7 Provide the structure of the intermediate which forms in the first step of the reaction of 1- butyne with water in the presence of H2SO4/HgSO4. 960119254831Answer: Section: 7-7 Provide the structure of the major organic product of the following reaction. Answer: Section: 7-7 Provide the major organic product in the reaction below. Answer: Section: 7-7 Give the major organic product for the reaction. 914400146109 A) 914400247943938530119126000B) C) 914400541059D) CH3CH2CH2CH CHOH E) Answer: A Section: 7-7 Give the best reagents for the reaction. H2SO4, HgSO4, HgSO4 1. disiamylborane, 2. HO-, H2O, H2O2 K2Cr2O7, H+ NaOCl 282085212427700H2, Pd Answer: A Section: 7-7 Which of the following is the final and major product of this reaction? I II III IV V Answer: C Section: 7-8 Which of the alkyne addition reactions below involves an enol intermediate? hydroboration/oxidation treatment with HgSO4 in dilute H2SO4 hydrogenation both A and B both A and C Answer: D Section: 7-7, 7-8 Provide the structure of the major organic product(s) in the reaction below. Answer: Section: 7-8 Complete the following reaction. Answer: ethynylcyclobutane Section: 7-8 95948521272500Provide the structure of the major organic product of the following reaction. Answer: Section: 7-8 91440023050500Provide the major organic product in the reaction below. Answer: Section: 7-8 MCAT: 9.2 Give the major organic product for the reaction. 32757163156500A) B) Answer: B Section: 7-8 Give the best reagents for the reaction. H2SO4, HgSO4, HgSO4 1. disiamylborane, 2. HO-, H2O, H2O2 K2Cr2O7, H+ NaOCl H2, Pd Answer: B Section: 7-8 Provide the structure of the major organic product that results when 2-butyne is treated with HgSO4/H2SO4 in water. Answer: Section: 7-7 The reagent needed to convert 2-butyne to cis-2-butene is H2/Pt. H2/Lindlar's catalyst. Li/NH3. Na/NH3. H+/Zinc dust. Answer: B Section: 7-9 The reagent needed to convert 2-butyne to trans-2-butene is H2/Pt. H2/Lindlar's catalyst. Li/NH3. Na/NH3. C or D. Answer: E Section: 7-9 A mixture of 1-heptyne, 2-heptyne, and 3-heptyne was hydrogenated in the presence of a platinum catalyst until hydrogen uptake ceased. If one assumes that the hydrogenation went to completion, how many distinct seven-carbon hydrocarbons were produced? 1 2 3 6 8 Answer: A Section: 7-9 In the reduction of alkynes using sodium in liquid ammonia, which of the species below is not an intermediate in the commonly accepted mechanism? vinyl anion vinyl radical radical anion vinyl cation Answer: D Section: 7-9 Provide the major organic product in the reaction below. Answer: Section: 7-9 An optically active compound (A), C6H10, reacts with H2/Ni to produce compound (B), C6H14. (B) is optically inactive. Deduce the structures of (A) and (B). 95948520066000Answer: Section: 7-9 Provide the structure of the major organic product(s) in the reaction below. Answer: Section: 7-9 1744217206287Provide the structure of the major organic product(s) in the reaction below. CH3CH2—C C—CH3 Answer: Section: 7-9 Complete the following reaction. 3-hexyne Answer: trans-3-hexene Section: 7-9 Provide the structure of the major organic product of the following reaction. Answer: Section: 7-9 Provide the structure of the major organic product of the following reaction. Answer: Section: 7-9 Provide the structure of the major organic product of the following reaction. Answer: Section: 7-9 Give the major organic product for the reaction. 204977414020300 38108301713600 C) CH3CH2CH2CH2CH3 B) C) 191021879387002386667611200 D) E) Answer: A Section: 7-9 Give the major organic product for the reaction. Answer: C Section: 7-9 Give the major organic product for the reaction. Answer: B Section: 7-9 Give the best reagents for the reaction. H2, Pd 1. LiAlH4, 2. H3O+ 1. NaBH4, 2. H3O+ H2, Lindlar catalyst Na, NH3 Answer: A Section: 7-9 Give the best reagents for the reaction. 1687716461500H2, Pd 1. LiAlH4, 2. H3O+ 1. NaBH4, 2. H3O+ H2, Lindlar catalyst Na, NH3 Answer: D Section: 7-9 Give the best reagents for the reaction. 168771613687700 H2, Pd 1. LiAlH4, 2. H3O+ 1. NaBH4, 2. H3O+ H2, Lindlar catalyst Na, NH3 Answer: E Section: 7-9 Provide the structure of the major organic product that results when 2-butyne is treated with H2 in the presence of Lindlar's catalyst. Answer: Section: 7-9 Which is the correct order of decreasing acidity in the following compounds? H2O CH3CH3 NH3 CH2 CH A B C D E A > E > C > D > B A > E > D > B > C E > A > C > B > D A > C > E > D > B E > D > B > A > C Answer: A Section: 7-10 1974342231433What are the products of the following reaction? CH3OH + CH3C C-Na+ ? ? CH3CCCH3 + NaOH CH3CCOCH3 + NaOH 149428256181CH3C CH + CH3O-Na+ CH3OCCH + NaCH3 no reaction Answer: C Section: 7-10 Which of the species below is less basic than acetylide? CH3Li CH3ONa NaOH both B and C all of the above Answer: D Section: 7-10 Among the compounds water, 1-butyne, 2-butyne, and ethane, which are stronger acids than ammonia? 1-butyne and ethane water and 1-butyne water and ethane 1-butyne and 2-butyne Answer: B Section: 7-10 What type of organic product results when 1-butyne is treated with 6M aqueous NaOH? a sodium acetylide an enol an alcohol an aldehyde Not much reaction; most of the alkyne remains unchanged. Answer: E Section: 7-10 Explain why N is a stronger acid than CH. Answer: Because nitrogen is more electronegative than carbon. Section: 7-10 Which hydrogens are more acidic, those of benzene or those of cyclohexane? Why? Answer: Benzene. The carbon hybridization of benzene is sp2 while that of cyclohexane is sp3. The more s character in benzene causes its hydrogens to be more acidic than those of cyclohexane. Section: 7-10 Why are terminal alkynes more acidic than other hydrocarbons? Answer: The carbanion which results upon deprotonation of a terminal alkyne has the lone pair of electrons in an sp hybrid orbital. The greater % s character of this orbital gives the orbital a significantly lower energy. Section: 7-10 For the reaction below indicate whether the equilibrium constant will be greater than 1 or less than 1. CH3Li + CH ? CH4 + CLi Answer: greater than 1 Section: 7-10 914400258087Provide the structure of the major organic product of the following reaction. Answer: Section: 7-10 MCAT: 9.2 For the reaction below indicate whether the equilibrium constant will be greater than 1 or less than 1. KOH + CH ? H2O + CK Answer: less than 1 Section: 7-10 95885017526000What is/are the major organic product(s) of the following reaction? CH2 CH2 + HC CH CH3CH2CCH HCCBr HCCCH2CH2Br CH3CCCH3 Answer: B Section: 7-11 Provide the structure of the major organic product(s) in the reaction below. 1834895-75652CH3CH2CH Answer: CCH2Ph Section: 7-11 Provide the structure of the major organic product of the following reaction. Answer: Section: 7-11 Give the major organic product for the reaction. 186499519621500 370663912884200 A) B) Answer: E Section: 7-11 Give the reagents for the following reaction. Answer: 1. NaNH2, 2. CH3CH2Br, 3. H2, Pd Section: 7-11 Provide the major organic product of the following reaction sequence. Answer: Section: 7-11 960119220765Suggest a plausible scheme for the following synthesis Answer: Section: 7-12 Describe a sequence of reactions by which 3-heptyne can be straightforwardly prepared from acetylene. Answer: NaNH2 CH3CH2Br NaNH2 CH3CH2CH2Br Section: 7-12 107) Describe a sequence of reactions by which meso-2,3-dibromobutane can be prepared from propyne. Answer: NaNH2 3) Na, NH3 CH3Br 4) Br2, CCl4 Section: 7-12 108) Describe a sequence of reactions by which butylbenzene can be prepared from phenylacetylene. Answer: NaNH2 CH3CH2Br H2, Pt Section: 7-12 109) Describe a sequence of reactions by which CH3CH2CH2COCH2CH3 can be prepared from 1-butyne. Answer: NaNH2 CH3CH2Br HgSO4, H2O, H2SO4 110) Describe a sequence of reactions by which trans-2-pentene can be prepared from propyne. Answer: NaNH2 CH3CH2Br Na, NH3 Section: 7-12 111) Describe a sequence of reactions by which the aldehyde CH3CH2CH2CH2CHO could be prepared from acetylene. Answer: NaNH2 3)disiamylborane CH3CH2CH2Br 4) H2O2, -OH Section: 7-12 112) Describe a sequence of reactions by which cis-2-pentene could be prepared from acetylene. Answer: NaNH2 CH3CH2Br NaNH2 CH3Br H2, Lindlar's catalyst Section: 7-12 Complete the following tree of reactions by giving the major products. Answer: Section: 7-12 Give the reagents for the following reaction. Answer: 1. H2, Lindlar catalyst or Na, NH3; 2. Br2 Section: 7-12 Give the reagents for the following reaction. Answer: 1. NaNH2, 2. CH3CH2Br, 3. disiamylborane, 4. HO-, H2O2, H2O Section: 7-12 Give the reagents for the following reaction. Answer: 1. NaNH2, 2. CH3CH2Br, 3. NaNH2, 4. CH3CH2Br, 5. 2 Br2 Section: 7-12 Provide the sequence of reagents that are needed to accomplish the multistep synthesis below. Answer: NaNH2 CH3CH2I H2, Lindlar catalyst Section: 7-12 Provide the sequence of reagents that are needed to accomplish the multistep synthesis below. Answer: NaNH2 CH3CH2I Na, NH3 Section: 7-12 Provide the major organic product of the following reaction sequence. Answer: Section: 7-12 2-butyne has higher boiling point than 2-butene because 2-butyne has stronger hydrogen bonds 2-butyne has stronger dipole dipole interactions 2-butyne has stronger london dispersion forces 2-butyne has triple bond which is harder to break 2-butyne has fewer hydrogens Answer: C Section: 7-4 The pi-bonds in ethyne is formed by end-to-end sp-sp overlap side-to-side sp-sp overlap end-to-end s-sp overlap end-to-end p-p overlap side-to-side p-p overlap Answer: E Section: 7-3 In the following molecule, how many bonds are formed by sp-s overlap? 0 1 2 3 4 Answer: B Section: 7-3 Keto-enol forms are resonance structures enantiomers disatereomers constitutional isomers conformational isomers Answer: D Section: 7-7 Why are mercuric ions needed during the hydration of alkynes? They catalyze the reaction by reacting with the alkyne and making it more nucleophilic. They catalyze the reaction by reacting with the alkyne and making it more electrophilic. They make alkynes more soluble in water. They increase the rate of addition reaction. B and D Answer: E Section: 7-7 95948526035000Draw both enol forms of the following molecule. Answer: Section: 7-7 In the hydroboration-oxidation reaction of a terminal alkyne, the product is a(n) alkyne aldehyde ketone enol alcohol Answer: B Section: 7-8 Dissolving metal reduction involves addition of H2O to a triple bond in the presence of Na in liquid NH3 addition of H2 to a triple bond in the presence of Na in liquid NH3 addition of H2O to a triple bond in the presence of NaNH2 in liquid NH3 addition of H2 to a triple bond in the presence of NaNH2 in liquid NH3 both B and D Answer: B Section: 7-9 Fill in the missing reagents 2 and 4 and the compound 3. Answer: Section: 7-10, 7-11 What is the structure of the missing product A and reagent B of this reaction? Answer: Section: 7-9 What is the structure of the missing reagents A and B below? Answer: 1 equivalent of Br2 Section: 7-6 Fill in the missing reagents A and B on both sides of the substrate. Answer: Reaction conditions: A H2, Lindlar's O3 Me2S Reaction Conditions: B 9-BBN, THF NaOH, H2O2, H2O Section: 7-12