Both isomers have exactly the same atoms in the same order. This means that the dispersion forces between the van der Waals molecules will be the same in both cases. The difference between the two is that the cis-isomer is a polar molecule, while the trans isomer is nonpolar.
There are two situations where you will encounter the terms “cis” and “trans”.
The first is in alkenes. Remember that we can not rotate Pi? This means that a molecule such as 2-butene will have two possible isomers; the isomer in which the two methyl groups are on the same side of the double bond is called “cis” and the isomer in which the two methyl groups are on the opposite side are called “trans”. A more generalized system for double bonds involves the Z-E system.
Cis – Same – “Zame”
Trans – Opposite – “Epposite”
When a molecule forms a ring, it blocks it to some extent. Think of a belt (or better, a dog collar). Before fixing it together, you can twist it as much as you like. But once you fix it, there are practical limits for how much you can turn it into. If the radius is too small (or the material too stiff!), Devine becomes “stuck”. You can not get him in. This describes the cyclical alkali situation that we will encounter most here.
So if two groups are on the same side of a ring, we use the same word: cis to describe it. And if I’m on the opposite side, we’ll use the word “trans” to describe it.
To show this, although we need a new visual terminology to describe how these molecules appear in 3D.
To display a group that indicates OUT of the page, we will use a closed Wedge line. To show a group that indicates IN to the page, we will use a dotted line “Dash”.
