Explanation:
The wavelength of a molecule is determined by the length of the conjugated system it contains. In simple terms, the more conjugated double bonds a molecule has, the longer its wavelength will be.
1,3-hexadiene and 1,4-hexadiene are both conjugated diene molecules, meaning they contain two double bonds that are conjugated (alternating single and double bonds).
1,3-hexadiene has the double bonds at positions 1 and 3 along the carbon chain: H2C=CH-CH=CH-CH3
1,4-hexadiene has the double bonds at positions 1 and 4 along the carbon chain: H2C=CH-CH2-CH=CH-CH3
In this case, 1,4-hexadiene would have a longer wavelength compared to 1,3-hexadiene. This is because in 1,4-hexadiene, the conjugated system extends over a longer distance along the carbon chain, resulting in a longer wavelength.
Therefore, 1,4-hexadiene would have the longest wavelength among the two molecules.