Organic chemistry: cis and trans

The tutor gives a simple explanation of why trans fat may be disadvantageous.

Cis and trans compounds have the same chemical formula but are shaped differently. With both cis and trans, a row of atoms experiences two irregularities.

The cis pattern navigates the two irregularities in such a way that it ends up on the same side whence it started. The letter “c” is a good way to think of “cis”: the letter starts and ends at the right.

The trans pattern ends up opposite whence it started. Letter “z” is a good illustration of the trans pattern: it starts at the left, but ends at the right.

I’ve heard that trans fat is to be avoided. (I’ve never heard that cis is better, just that trans is not preferred.) The reason, as I understand, is that trans fat molecules, because of their zigzag geometry, stack alongside each other more easily than do cis fat molecules. Since the trans fat molecules stack together more easily, they can be more difficult to separate as well. Therefore, they have a stronger potential to form layers inside blood vessels.

Cis and trans are examples of isomerism. Isomers are molecules with the same formula but different arrangment of the atoms. Organic chemistry has so much focus on isomerism, I could easily write twenty posts about it. I may, in time….

HTH:)

Source:

Solomons, T.W. Graham. Organic Chemistry, 4th ed. Toronto: John Wiley &Sons, 1988.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

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