Chapter 10 Alkynes Assembling the Systematic Name of an Alkyne

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Gertrude Fowler
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1 hapter 10 Alkynes eview of oncepts Fill in the blanks below. To verify that your answers are correct, look in your textbook at the end of hapter 10. Each of the sentences below appears verbatim in the section entitled eview of oncepts and Vocabulary. A triple bond is comprised of three separate bonds: one bond and two bonds. Alkynes exhibit geometry and can function either as bases or as. Monosubstituted alkynes are terminal alkynes, while disubstituted alkynes are alkynes. atalytic hydrogenation of an alkyne yields an. A dissolving metal reduction will convert an alkyne into a alkene. Acid-catalyzed hydration of alkynes is catalyzed by mercuric sulfate to produce an that cannot be isolated because it is rapidly converted into a ketone. Enols and ketones are, which are constitutional isomers that rapidly interconvert via the migration of a proton. When treated with ozone, followed by water, internal alkynes undergo oxidative cleavage to produce. Alkynide ions undergo when treated with an alkyl halide (methyl or primary). eview of Skills Fill in the blanks and empty boxes below. To verify that your answers are correct, look in your textbook at the end of hapter 10. The answers appear in the section entitled SkillBuilder eview Assembling the Systematic Name of an Alkyne PVIE A SYSTEMATI NAME F TE FLLWING MPUN 1) IENTIFY TE PAENT 2) IENTIFY AN NAME SUBSTITUENTS 3) ASSIGN LANTS T EA SUBSTITUENT 4) ALPABETIZE 10.2 Predicting the Position of Equilibrium for the eprotonation of a Terminal Alkyne ILE TE SIE F TE EQUILIBIUM TAT IS FAVE IN TE FLLWING AI-BASE EATIN + + 2

2 204 APTE rawing the Mechanism of Acid-atalyzed Keto-Enol Tautomerization AW TW UVE AWS SWING PTNATIN F TE πbn AW TE ESNANE STUTUES F TE INTEMEIATE AW TW UVE AWS SWING EPTNATIN T FM TE KETNE 10.4 hoosing the Appropriate eagents for the ydration of an Alkyne IENTIFY EAGENTS TAT AN AIEVE EA F TE FLLWING TANSFMATINS 1) 2) 10.5 Alkylating Terminal Alkynes IENTIFY EAGENTS TAT WILL AIEVE TE FLLWING TANSFMATIN: 1) 2) 3) 4) 10.6 Interconverting Alkanes, Alkenes, and Alkyne IENTIFY EAGENTS TAT WILL AIEVE TE FLLWING TANSFMATINS: 1) 2) 3) 1) 2)

3 APTE eview of eactions Identify the reagents necessary to achieve each of the following transformations. To verify that your answers are correct, look in your textbook at the end of hapter 10. The answers appear in the section entitled eview of eactions. X X X X X 3 X X X X X X + Solutions hexyne 2-methyl-3-hexyne c) 3-octyne d) 3,3-dimethyl-1-butyne

4 206 APTE hexyne 3-methyl-1-pentyne 4-methyl-1-pentyne 3,3-dimethyl-1-butyne Yes, NaN 2 is strong enough of a base to deprotonate a terminal alkyne. No, NaEt is not strong enough of a base to deprotonate a terminal alkyne. c) No, Na is not strong enough of a base to deprotonate a terminal alkyne. d) Yes, BuLi is strong enough of a base to deprotonate a terminal alkyne. e) Yes, Na is strong enough of a base to deprotonate a terminal alkyne. f) No, t-buk is not strong enough of a base to deprotonate a terminal alkyne In the conjugate base of methyl amine ( 3 N 2 ), the negative charge is associated with an sp 3 hybridized nitrogen atom. In the conjugate base of N, the negative charge is associated with an sp hybridized carbon atom. The latter is more stable, because the charge is closer to the positively charged nucleus. As a result, N is a stronger acid than methyl amine. The pk a of N is lower than the pk a of a terminal alkyne. Therefore, cyanide cannot be used as a base to deprotonate a terminal alkyne, as it would involve the formation of a stronger acid. + NaN Na + weaker acid N stronger acid

5 APTE N 2 N 2 N 2 l l N 2 N 2 l N 2

6 208 APTE N 2 2-pentyne N 2 N N N 2 Formation of the alkynide ion pushes the equilibrium to favor isomerization 1-pentyne alkynide ion Lindlar's catalyst 2 Pt 2 Ni 2 B 2 Ni c) d)

7 APTE Lindlar's catalyst Na N 3 (l) Na N 3 (l) 2 Pt xs l l l l 1) xs NaN 2 / N 3 l 2) 2 c) xs d) 1) xs NaN 2 / N 3 2) 2 e) l l 1) xs NaN 2 / N 3 2) 2 + 3), f) l l 1) xs NaN 2 / N 3 2) 2 3) excess

8 210 APTE l l 1) xs NaN 2 / N 3 2) 2 3) excess l l l If two products are obtained, then the alkyne must be internal and unsymmetrical. There is only one such alkyne with molecular formula 5 8 : xs c) d)

9 APTE N N N N N N N N c) d) e) c) ) 9-BBN 2) 2 2, Na 1) isiamylborane 2) 2 2, Na c) 1) 9-BBN 2) 2 2, Na

10 212 APTE c) S 4, 2 gs 4 1) 9-BBN or disiamylborane 2) 2 2, Na ) xs NaN 2 2) 2 3) 9-BBN or disiamylborane 4) 2 2, Na l l 1) xs NaN 2 2) 2 3) 2 S 4, 2, gs ) 2 2) xs NaN 2 3) 2 4) 2 S 4, 2, gs ) 3 2) 2 + 1) 3 2) 2 +

11 APTE c) 1) 3 2) 2 + d) 1) 3 2) If ozonolysis produces only one product, then the starting alkyne must be symmetrical. There is only one symmetrical alkyne with molecular formula 6 10 : 1) 3 2) S 4, 2 gs ) NaN 2 2) EtI 1) NaN 2 2) MeI 3) NaN 2 4) MeI c) 1) NaN 2 2) EtI 3) NaN 2 4) EtI

12 214 APTE 10 d) 1) NaN 2 2) 3) NaN 2 4) MeI I e) 1) NaN 2 2) I f) 1) NaN 2 2) 3) NaN 2 4) MeI I g) 1) NaN 2 2) 3) NaN 2 4) EtI I h) 1) NaN 2 2) 3) NaN 2 4) MeI I i) 1) NaN 2 2) EtI 3) NaN 2 4) MeI j) 1) NaN 2 2) EtI 3) NaN 2 4) I

13 APTE k) 1) NaN 2 2) I 3) NaN 2 4) I This process would require the used of a tertiary substrate, which is not reactive toward S N octyne ) 2, Lindlar's catalyst 2) (Et) 1) NaN 2 2) Et 3) NaN 2 4) Et ) 2 2) xs NaN 2 3) 2 4) NaN 2 5) EtI 6) 2, Lindlar's catalyst Note: The alkyne produced after step 3 does not need to be isolated and purified, and therefore, steps 3 and 4 can be omitted. 1) 2 2) xs NaN 2 3) 2 4) 9-BBN 5) 2 2, Na

14 216 APTE 10 1) 2, Lindlar's catalyst c) 2) dilute 2 S 4 d) 1) 2, Lindlar's catalyst 2) B 3 TF 3) 2 2, Na 1) NaN 2 2) EtI 3) Na, N 3 (l) e) 4) 2 1) NaN 2 2) EtI 3) 2, Lindlar's catalyst + En f) 4) ) NaEt 2) 2 3) xs NaN 2 4) 2 5) 3 6) 2 2 1) NaEt 2) 2 3) xs NaN 2 4) 2 5) NaN 2 6) MeI 7) 3 8) 2 Note: The alkyne produced after step 4 does not need to be isolated and purified, and therefore, steps 4 and 5 can be omitted.

15 APTE ) 2, Lindlar's catalyst 2) (Et) 1) 2 2) xs NaN 2 3) 2 1) NaN 2 2) Et 3) NaN 2 4) Et 2 S 4, 2 gs ,2,5-trimethyl-3-hexyne 4,4-dichloro-2-hexyne c) 1-hexyne d) 3-bromo-3-methyl-1-butyne c)

16 218 APTE Lindlar's at. 2 Pt Na N 3 (l) 2 Ni 2 B 2 Pd Na N 3 (l) Lindlar's at. 2 Pt Na + Na + 2

17 APTE c) d) e) 2 S 4, 2 gs 4 1) 9-BBN 2) 2 2, Na (2 eq) l (1 eq) 2 (2 eq) l 4 l 1) NaN 2, N 3 f) 2) MeI 2 g) Pt l 2 Pt l (1 eq) 2 Lindlar's catalyst (xs) 1) 3 2) 2 1) 9-BBN 2) 2 2, Na 2 S 4 2 gs No Yes c) Yes d) No e) Yes

18 220 APTE No. These compounds are constitutional isomers, but they are not keto-enol tautomers because the pi bond is not adjacent to the group. Yes c) Yes d) Yes c) Lindlar's catalyst Na N 3 (l) leic Acid Elaidic Acid ) excess NaN 2 2) Etl 3) 2, Lindlar's atalyst 1) NaN 2 2) MeI 3) 9-BBN 4) 2 2, Na c) 1) NaN 2 2) EtI 3) gs 4, 2 S 4, 2

19 APTE d) 1) NaN 2 2) MeI 3) NaN 2 4) EtI 5) Na, N 3 (l) When ()-4-bromohept-2-yne is treated with 2 in the presence of Pt, the asymmetry is destroyed and 4 is no longer a chirality center: 2 Pt not a chirality center This is not the case for ()-4-bromohex-2-yne ethyl-1-pentyne Na N Na N

20 222 APTE NaN 2 Na l N ompound A 2 Pd ompound A has two chirality centers: 2,4,6-trimethyloctane c) The locants for the methyl groups in ompound A are 3, 5, and 7, because locants are assigned in a way that gives the triple bond the lower possible number (1 rather than 7) ) 9-BBN 2) 2 2, Na ompound A

21 APTE ) NaN 2 2) EtI 3) 2 S 4, 2, gs 4 1) excess NaN 2 2) 2 3) 2, Lindlar's atalyst c) 1) excess NaN 2 2) 2 3) NaN 2 4) MeI 5) Na, N 3 Note: The alkyne produced after step 2 does not need to be isolated and purified, and therefore, steps 2 and 3 can be omitted. d) 1) excess NaN 2 l l 2) 2 3) 2 S 4, 2, gs 4 e) 1) excess NaN 2 2) 2 3) 2 (1 eq) f) 1) excess NaN 2 2) 2 l l 3) 2, Lindlar's atalyst 4) dilute 2 S S 4, 2 gs 4

22 224 APTE If two products are obtained, then the alkyne must be internal and unsymmetrical. There is only one such alkyne with molecular formula 5 8 : 2 S 4, 2 gs c) 1) 2 2) excess NaN 2 3) 2 1) 2 2) excess NaN 2 3) 2 4) 2 S 4, 2, gs 4 1) NaN 2 2) EtI 3) Na, N 3 (l) d) 1) NaN 2 2) 3) 2, Pt I l l l l

23 APTE ) excess NaN 2 2) 2 NaN 2 I Na ) Na, N 3 (l) 2) 2 1) 2, Lindlar's atalyst + En 2) 2 c) 1) Na, N 3 (l) 2) s 4, NM + En 1) 2, Lindlar's atalyst 2) MPBA 3) 3 + d) 1) Na, N 3 (l) 2) MPBA 3) 3 + 1) 2, Lindlar's atalyst 2) s 4, NM

24 226 APTE 10 e) 1) NaN 2 2) MeI 3) NaN 2 4) MeI 5) Na, N 3 (l) 6) s 4, NM + En 1) NaN 2 2) MeI 3) NaN 2 4) MeI 5) 2, Lindlar's atalyst 6) MPBA 7) 3 + f) 1) NaN 2 2) MeI 3) NaN 2 4) MeI 5) Na, N 3 (l) 6) MPBA 7) 3 + 1) NaN 2 2) MeI 3) NaN 2 4) MeI 5) 2, Lindlar's atalyst 6) s 4, NM Lindlar's atalyst Na N 3 (l)

25 APTE c) 1) NaN 2 2) N 2 3 I N N 3 N N

26 228 APTE ) 2, Lindlar's catalyst 2) (Et) 1) NaN 2 2) Et 3) NaN 2 4) Me 1) Na, N 3 (l) 2) MPBA Et Me + En 1) 2, Lindlar's catalyst 2) (Et) 1) NaN 2 2) Et 3) NaN 2 4) Me 1) 2, Lindlar's atalyst 2) MPBA Et Me + En

27 APTE

Chapter 22 Carbonyl Alpha-Substitution Reactions

John E. McMurry www.cengage.com/chemistry/mcmurry Chapter 22 Carbonyl Alpha-Substitution Reactions The α Position The carbon next to the carbonyl group is designated as being in the α position Electrophilic