Isomerism and StereochemistryhardNUMERICAL

Calculate the total number of distinct geometrical isomers possible for the symmetrical polyene chaiIsomerism and Stereochemistry Chemistry Question

Question

Calculate the total number of distinct geometrical isomers possible for the symmetrical polyene chain: $CH_3-CH=CH-CH=CH-CH_3$.

Answer: 3

💡 Solution & Explanation

The molecule is symmetrical (the structural ends are identical) and contains an even number of stereogenic double bonds ($n=2$). The standard mathematical formula for total geometrical isomers in a symmetrical even system is $2^{(n-1)} + 2^{(n/2 - 1)}$. Substituting $n=2$: $2^{(2-1)} + 2^{(2/2 - 1)} = 2^1 + 2^0 = 2 + 1 = 3$.

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