Starting with ethyne, outline syntheses of each of the...

Starting with ethyne, outline syntheses of each of the following. You may use any other needed reagents, and you need not show the synthesis of compounds prepared in earlier parts of this problem. (a) Propyne (b) 1 -Butyne (c) 2 -Butyne (d) cis-2-Butene (e) trans- 2 -Butene (f) 1 -Pentyne (g) 2 -Hexyne (h) $(Z)$ - 2 -Hexene (i) $(E)-2$ -Hexene (j) 3 -Hexyne (k) $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{C}=\mathrm{CD}$ (l) (FIGURE CANNOT COPY)

Starting with ethyne, outline syntheses of each of the following. You may use any other needed reagents, and you need not show the synthesis of compounds prepared in earlier parts of this problem.
(a) Propyne
(b) 1 -Butyne
(c) 2 -Butyne
(d) cis-2-Butene
(e) trans- 2 -Butene
(f) 1 -Pentyne
(g) 2 -Hexyne
(h) $(Z)$ - 2 -Hexene
(i) $(E)-2$ -Hexene
(j) 3 -Hexyne
(k) $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{C}=\mathrm{CD}$
(l) (FIGURE CANNOT COPY)

Key Concepts

Acetylide Anion Formation

A terminal alkyne, such as ethyne, can be deprotonated using a strong base to form a nucleophilic acetylide anion. This deprotonation is a key step in many synthetic strategies because the acetylide ion is a highly reactive species that can effectively attack electrophilic centers, thereby enabling carbon–carbon bond formation without the need for metal catalysts in the initial activation step.

Alkylation of Alkynes

Once the acetylide ion is formed, it can undergo SN2 reactions with primary alkyl halides, a process which extends the carbon skeleton of the molecule. This alkylation reaction is critical in organic synthesis for constructing more complex alkyne molecules, achieving chain elongation, and allowing for precise placement of substituents, leading to various regioisomers depending on the electrophile employed.

Stereoselective Hydrogenation

Alkynes can be partially reduced to alkenes in a stereoselective manner. When using a poisoned catalyst like Lindlar’s catalyst, hydrogenation of an alkyne typically yields a cis-alkene, while alternative conditions such as dissolving metal reductions (e.g., sodium in liquid ammonia) favor the formation of trans-alkenes. This selectivity is crucial for synthesizing alkenes with a defined stereochemistry from alkynes.

Isotopic Labeling in Organic Synthesis

The incorporation of isotopes such as deuterium into organic molecules is a valuable tool in mechanistic studies and tracer experiments. In synthetic procedures, specific positions within a molecule can be selectively replaced with deuterium using deuterated reagents, thereby allowing chemists to track reaction dynamics or modify the physical properties of the molecule without significantly altering its chemical reactivity.

Transcript

00:01 So we're continuing to look at our reactivity of our alkenes and our alkynes.

00:04 What we're starting off with is a thylene in the presence of n -a, nh2, liquid ammonia, nh3.

00:18 What we form is hc, triple bond, c, formal negative charge, and a plus.

00:28 We then have missile iodide, it's form proponine.

00:33 Now next example we have a cyanide where our carbon has a formal negative charge an allurempair.

01:02 Following reagents yields butte 1ine.

01:16 Following this we can take probe 1ine treat it with n -a, nh2, liquid ammonia, nh3.

01:37 What we generate is the following methyl iodide to generate our product that is bute 2 -eine next we have bute 2 -ine then we have lindelars catalyst where you generate the cyst tube butine following this we have our boot -toine starting material again using l -i -e -t -nh3 negative 78 degrees celsius and nh4 cl we can generate the transbutte wene so in contrast to lindelar's catalyst which only generates the sis, we can have the trans alkene here.

03:05 So you can see the comparison of those two materials where we have the siss and the trans.

03:31 Next example, what we have is thionide harding material.

03:44 Treat it with ch3, ch2, ch2, ch2i.

03:51 We then generate pent1ine.

03:53 Following this we can take our pent one ian treat this with n a n h2 liquid ammonia n h3 generate pent one ian one i'd you have the addition of methyl iodide so of hex 2 ian next we can take hex 2 ian treat it with lindlas catalyst we will generate cis alkyne.

05:21 Now if we wanted the trans, we can also generate that using the reagents that we had above, these reagents here...

Please give Ace some feedback