Isomeric hydrocarbons → negative Baeyer’s test

(Molecular formula C₉H₁₂)

The total number of isomers from above with four different non-aliphatic substitution sites is -

The sum of sigma (σ) and pi (π) bonds in Hex-1,3-dien-5-yne is ________.

The compound with molecular formula $\mathrm{C}_6 \mathrm{H}_6$, which gives only one monobromo derivative and takes up four moles of hydrogen per mole for complete hydrogenation has _________ $\pi$ electrons.

Major product B of the following reaction has ________ $$\pi$$-bond.