chem naming of organic cpds

你的 case 是cyclohexa-1,4-diene also known as 1,4-cyclohexadiene Molecular formula 是C6H8 http://www.chemspider.com/Chemical-Structure.11838.html cyclohexa-1,4-diene is a derivative of cyclohexane C6H12cyclohexane is a saturated monocyclic hydrocarbon (with no side chains) The names of unsaturated monocyclic hydrocarbons are formed by substituting “-ene,” “-adiene,”“-atiene,”. etc., for ‘-ane” in the name of corresponding cycloalkane. The chain is so numbered as to give the lowest numbers to the double bonds. cyclohexane -> cyclohexenecyclohexane -> 1,4- cyclohexadiene
You have to learn the IUPAC rules for naming organic compounds.
你的問題是化學問題從英文角度去, 只有說cyclo- 是 prefix meaning a molecule consisting of atoms in a ring.In cycloalkane, the carbon atoms are joined up in a ring, hence cyclo

diene 是 two carbon double bonds, C=C and C=Chex 是 six carbon atoms (met -1, eth -2, prop – 3, but = 4, pent – 5, hex -6)

2015-07-30 00:00:13 補充：
Straight-chain alkanes take the suffix "-ane" and are prefixed depending on the number of carbon atoms in the chain, following standard rules.

Correction
For one carbon atom, the prefix is "meth-", not "met-"

methane, ethane, propane, butane, pentane, hexane

"hexa-" is used to form compound words with the sense of "six".as in "cyclohexa-1,4-diene"
"hex-" is the alternative form of hexa- when used before a vowel. eg hexose