Organic Chemistry

260 CHAPTER 6 Reactions of Alkynes • Introduction to Multistep Synthesis

2. Addition of hydrogen (Section 6.8)


3. Removal of a proton, followed by alkylation (Sections 6.9 and 6.10)

NaNH 2 R′CH 2 Br

RC CH RC C− RC CCH 2 R′

RC CR′ + 2 H 2 RCH 2 CH 2 R′

Pd/C, Pt/C,

or Ni

RHCC 2 C

H H

R R′

R′ + C

Lindlar

catalyst

RCC C

R H

H R′

R′ C

Na or Li

NH 3 (liq)

Key Terms

acetylide ion (p. 252)

aldehyde (p. 246)

alkylation reaction (p. 253)

alkynes (p. 238)

carbonyl group (p. 246)

enol (p. 246)

geminal dihalide (p. 243)

internal alkyne (p. 239)

keto–enol tautomers (p. 246)

ketone (p. 246)

polymers (p. 258)

radical anion (p. 250)

retrosynthetic analysis (p. 255)

tautomerization (p. 246)

tautomers (p. 246)

terminal alkyne (p. 239)

vinylic cation (p. 243)

vinylic radical (p. 250)

Problems

22. Give the major product obtained from reaction of each of the following with excess HCl:


23. Draw a structure for each of the following:
    a. 2-hexyne g. 1-bromo-1-pentyne
    b. 5-ethyl-3-octyne h. propargyl bromide
    c. methylacetylene i. diethylacetylene
    d. vinylacetylene j. di-tert-butylacetylene
    e. methoxyethyne k. cyclopentylacetylene
    f. sec-butyl-tert-butylacetylene l. 5,6-dimethyl-2-heptyne


24. Identify the electrophile and the nucleophile in each of the following reaction steps. Then draw curved arrows to illustrate the
    bond-making and -breaking processes.

CH 3 CH 2 CCH+ 2 +

+

C1 CH 3 CH 2 CCH 2

C1

CH 3 CHBrCH + CH 3 CCH 2 + Br–

CH 3 C CH+ –NH 2

• CH 3 CC + NH 2


• 
  

a.CH 3 CH 2 CCH b.CH 3 CH 2 C CCH 2 CH 3 c.CH 3 CH 2 C CCH 2 CH 2 CH 3

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