between butane,cis-2-butane,2-butyne,ethane and trans-2-butene which one has higher melting

What in the world is cis-2-butane?

I looked the melting points up on the web. Assuming you meant cis-2-butENE and not cis-2-butane(I don't know what this is). I found 2-butyne to have the highest m.p. @ -32 C

To determine which compound has a higher melting point among butane, cis-2-butane, 2-butyne, ethane, and trans-2-butene, we need to consider their molecular structures and intermolecular forces.

The intermolecular forces are responsible for holding molecules together in a solid or liquid state. The strength of these forces affects the melting point of a substance. The stronger the intermolecular forces, the higher the melting point.

Let's analyze each compound one by one:

1. Butane (C4H10): It is an alkane with a straight chain and no functional groups. The only intermolecular force acting between butane molecules is London dispersion forces. These forces are relatively weak, so butane has a low melting point.

2. cis-2-Butane: This compound has the same chemical formula as butane but differs in the arrangement of its atoms. It contains a double bond, which introduces some polarity. The dipole-dipole forces, along with dispersion forces, are present. These intermolecular forces are slightly stronger than in butane, but still relatively weak.

3. 2-Butyne (C4H6): This compound contains a triple bond, making it more polar than both butane and cis-2-butane. The presence of triple bonds allows for stronger dipole-dipole interactions, resulting in higher intermolecular forces and a higher melting point than the previous two compounds.

4. Ethane (C2H6): It is an alkane with a linear structure like butane but contains fewer carbon atoms. Ethane has similar intermolecular forces as butane, dominated by dispersion forces, due to its nonpolar nature. Therefore, it has a lower melting point than butane, cis-2-butane, and 2-butyne.

5. trans-2-Butene: This compound contains a double bond, contributing to some polarity. It exhibits stronger dipole-dipole forces compared to butane and cis-2-butane. However, these forces are not as strong as the dipole-dipole forces in 2-butyne. Therefore, trans-2-butene has a higher melting point than butane and cis-2-butane but lower than 2-butyne.

In summary, among butane, cis-2-butane, 2-butyne, ethane, and trans-2-butene, 2-butyne has the highest melting point due to the presence of stronger intermolecular forces resulting from its triple bond.