Alkynide Synthesis Practice Problems

Why alkynide alkylation reaction shown below fails to yield the desired product? What actual major product would be formed in this reaction?

Why the following S_N2 reaction of 1° bromide by alkynide fails to give the desired product?

Draw the conformer that predominates at equilibrium for the compound given below.
1,2-dibromoethane

Determine the energy difference (in kJ/mol) between the least stable staggered conformer and the least stable eclipsed conformer for the compound given below.

1,2-dibromoethane

Note: A gauche conformer has two energy barriers, 22.6 kJ/mol and 39.7 kJ/mol. The anti conformer is 5.86 kJ/mol more stable than a gauche conformer.

Determine the energy difference (in kJ/mol) between the most stable eclipsed conformer and the most stable staggered conformer for 1,2-dibromoethane.

Note: A gauche conformer has two energy barriers, 22.6 kJ/mol and 39.7 kJ/mol. The anti conformer is 5.86 kJ/mol more stable than the gauche conformer.

Starting with the least stable conformer, draw an appropriate potential energy diagram for rotation about the C−C bond of 1,2-dibromoethane through 360º if a gauche conformer of 1,2-dibromoethane has two energy barriers, 5.4 kcal/mol and 9.5 kcal/mol, and the anti conformer is more stable than a gauche conformer by 1.4 kcal/mol.

Show the synthesis of non-4-yne by adding the butyl group and the propyl group afterward. Give all the reagents and intermediates.

Using acetylene as the starting material, show how each of the following compounds can be synthesized. In your synthesis, you can use any compounds with four or less carbon atoms.
(i) but-1-yne
(ii) but-2-yne
(iii) cis-but-2-ene

Using acetylene as the starting material, show how each of the following compounds can be synthesized. In your synthesis, you can use any compounds with four or less carbon atoms.
(i) trans-but-2-ene
(ii) 1,1-dibromobutane
(iii) 2,2-dibromobutane

Using acetylene as the starting material, show how each of the following compounds can be synthesized. In your synthesis, you can use any compounds with four or less carbon atoms.
(i) propanal
(ii) acetone
(iii) (±) 2,3-dibromobutane