Question

How do you convert ethanol to but-2-yne?

Reactions that might be helpful:

Halogenation

R-OH + P/ `X_2` → R-X

Dehydrohalogenation

Finkelstein Reaction

CH3CH2Br (acetone) + NaI (acetone) → CH3CH2I (acetone) + NaBr (s)

Wurtz Reaction

2R–X + 2Na → R–R + 2Na+X−

Electrophilic Addition,
Nucleophilic Substitution

Answer 1

How about this?

Explanation:

1. Halogenation

`"CH"_3"CH"_2"-OH" stackrelcolor(blue)("P/Br"_2color(white)(mm))(→) "CH"_3"CH"_2"-Br"`

2. Dehydrohalogenation

`"CH"_3"CH"_2"-Br" stackrelcolor(blue)("alc. KOH," Δcolor(white)(mm))(→) "H"_2"C=CH"_2`

3. Electrophilic addition

`"H"_2"C=CH"_2 stackrelcolor(blue)("Br"_2color(white)(mm))(→) "Br-CH"_2"-CH"_2"-Br"`

4. Dehydrohalogenation

`"Br-CH"_2"-CH"_2"-Br" stackrelcolor(blue)("Na, liq. NH"_3color(white)(mm))(→) "Na"^"+"stackrelcolor(blue)("-")("C")≡stackrelcolor(blue)("-")("C")"Na"^"+"`

5. Nucleophilic substitution

#"Na"^"+"stackrelcolor(blue)("-")("C")≡stackrelcolor(blue)("-") ("C")"Na"^"+" stackrelcolor(blue)("CH"_3"Br"color(white)(mm))(→) "CH"_3"C≡CCH"_3#