styles in numbering & naming molecules

styles in numbering & naming molecules


Hello from Chem Help ASAP. As it turns out, there are different styles
in how you number molecule and how you show those numbers in the names. Let’s talk about those styles, or two common
styles. On the screen, on the left, we have three
different molecules. I have numbered them. Actually, there’s not a difference in how you
number the molecules – number them for naming. It’s the same regardless of your style. But, I’ve written in the middle of the screen,
my style that I have presented in these videos. This is actually a really common style. There is however a newer style that has come
on the scene. When I say newer, I am talking about 15-20
years ago. It’s not that new. But, you’re going to encounter this probably
if you look at names of molecules. What you tend to do in this newer style is,
you tend to put the number as close to the indicator of the functional group in the name
as possible. So, instead of saying 1-pentanol, you would
say pentan-1-ol – to get that number 1 right up next to that “ol”. So, it’s very clear what the 1 is referring
to. You do this with alkenes as well. Instead of saying 1-pentene, you’d say pent-1-ene. Again, to get the number as close to the functional
group as possible. This also applies to a molecule like the bottom
one. 4-penten-1-ol. Instead of having that 4 dangling out in front
and it’s maybe a little bit ambiguous to you what it refers to, let’s just put it right
in front of the alkene. So, this would be pent-4-en-1-ol. Then it’s very clear. The alkene is with the 4. The alcohol is with the 1. Anytime you’re dealing with style, my style
is not important. It’s really the style of your instructor that
is important. Always – if you’re using these videos to supplement
what you’re learning in the classroom – always, always follow the style of your instructor,
because your instructor is the person who is evaluating you, and your instructor is
trying to model the behavior of a chemist to you. So, follow that lead. However, if you’re casually learning, note
that you will encounter different styles and you’re going to have to work with those. Definitely, follow your instructor’s style.

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