Nomenclature

[jenna111382]

Hi- does anyone know whether an alcohol takes priority over a halogen? I would think so because they are higher priority than double bonds, but wanted to be sure. (So in other words, if an alkane had a halogen and an alcohol, the alcohol would get a lower number.) Thanks!

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[161927]

A halogen has a higher priority than an oxygen because a halogen has a greater molecular weight.

 

[jenna111382]

Not to be argumentative, but I looked it up and I think MW only has to do with R and S configurations- for naming alcohols I am pretty sure the carbon with the OH receives the lowest number- I can give you a link if you'd like.

 

[161927]

Not to be argumentative, but I looked it up and I think MW only has to do with R and S configurations- for naming alcohols I am pretty sure the carbon with the OH receives the lowest number- I can give you a link if you'd like.

An alcohol substituent has a higher priority than a halogen, yes. I incorrectly assumed you were talking about R/S configurations.

Someone posted a question today dealing with CH2ClCH3OH. This molecule would be named 2-chloroethanol (or 2-chloroethan-1-ol to make explicit the priority order OH > Cl).

 

[Farcus]

to add to this, does a hydroxy group have higher priority other functional groups like say a methyl group, a carboxylic acid, an amine group?

 

[cavalier329]

i believe the hydroxyl has the highest priority

 

[jenna111382]

I think Carboxyllic acid (or any carbonyl) is the highest priority, followed by an alcohol subsituent.

 

[fmaemc2]

most oxidized functional group always gets priority. COOH beats OH.