Which of the following six-carbon molecules can be a straight-chain alkyne with two triple bonds and no double bonds?

C6H4
C6H6
C6H8
C6H10

A triple bond has two degrees of unsaturation, each. So, you have four degrees of unsaturation.

So use the following equation:

Degrees of unsaturation=(2n+2-H)/2

You know that you have four degrees of unsaturation, and you know that you must have 6 carbons (n). So, solve for the number of hydorgens that you will have.

4=(2(6)+2-H)/2

8=12+2-H
-6=-H
H=6

So, C6H6

To determine which of the four molecules can be a straight-chain alkyne with two triple bonds and no double bonds, we need to find the possible combinations of carbon-carbon bonds that satisfy these criteria.

The formula for straight-chain alkanes without any double or triple bonds is CnH2n+2, where n is the number of carbon atoms.

For an alkyne, we replace two of the carbon-carbon single bonds in an alkane with two triple bonds. Therefore, the formula for a straight-chain alkyne with two triple bonds is CnH2n-2.

Now let's analyze each molecule:

1. C6H4: This molecule doesn't have enough hydrogen atoms to match the formula for an alkyne. It has four hydrogens, but according to the formula CnH2n-2, we need six hydrogens.

2. C6H6: This molecule represents benzene, which is an aromatic compound. Benzene has alternating double bonds between carbon atoms and can't fulfill the requirement of having two triple bonds and no double bonds.

3. C6H8: This molecule has six carbon atoms and eight hydrogen atoms. By applying the formula CnH2n-2, we find that it matches the formula for a straight-chain alkyne with two triple bonds. Therefore, C6H8 can be a straight-chain alkyne with two triple bonds and no double bonds.

4. C6H10: This molecule also has six carbon atoms, but it contains ten hydrogen atoms. According to the formula CnH2n-2, it should only have eight hydrogens. Thus, C6H10 can't be a straight-chain alkyne with two triple bonds and no double bonds.

In conclusion, out of the given options, only C6H8 can be a straight-chain alkyne with two triple bonds and no double bonds.