Chemistry 3/4 2013 Thread

[barydos]

It would be A.

Convention - alphabetical order. Letter 'a' comes before 'm' in the alphabet.

Great, you definitely live up to your name - you're a star.
Cheers mate!

[jgoudie]

What you are looking at here is understanding the priority of the numbering system:

In general:

The suffix will have a greater priority (ie. -COOH, -OH, -NH₂, C=C, alkynes)

The prefixes (alkyl groups and halogens) have equal priority. We just go with the smallest numbers.

This is simplified, check the link for greater detail:
http://www.chem.ucalgary.ca/courses/350/Carey5th/useful/nomen.html

The functional group takes priority.

Example 1) Number carbon atoms from the right

Example 2) Number carbon atoms from the left (as you have done)

[Homer]

is CF2Cl2 a organic compound if so how would you name it?

[teletubbies_95]

I think it's dichloro difluro methane !
Hope that helps !

[Homer]

 would CH3(CH2)3CHOHCH3  be 5- hexanol or 2- hexanol?

also how would you name CHCl2CHBr2

[teletubbies_95]

The OH- functional group ( in any case , the functional group always is the first priority ) , when naming , therefore it would be 2 hexanol.

dichloro dibromo ethane !  

[lzxnl]

would CH3(CH2)3CHOHCH3  be 5- hexanol or 2- hexanol?

also how would you name CHCl2CHBr2

For the second one, there are two carbons, so parent alkane is ethane. Two bromines on one carbon, two chlorines on the other, we have 1-dibromo-2-dichloroethane. As bromo and chloro groups have the same priority, you order them alphabetically without the "di" numbering prefix. I think teletubbies_95 just overlooked the extra sneaky carbon in the middle there.

As for the first one, 2-hexanol is fine, but honestly hexan-2-ol, which looks messy, makes more sense as you now know what the 2 refers to. It's like when we say 2-methylbutane; 2- in front of the methyl that it refers to.

[Aurelian]

For the second one, there are two carbons, so parent alkane is ethane. Two bromines on one carbon, two chlorines on the other, we have 1-dibromo-2-dichloroethane. As bromo and chloro groups have the same priority, you order them alphabetically without the "di" numbering prefix.

You need to specify the positions of each halo substituent. Thus the correct name is 1,1-dibromo-2,2-dichloroethane rather than simply 1-dibromo-2-dichloroethane.

[lzxnl]

Oops. I stand corrected. Yeah I completely forgot about the second halogen in each one.

[Homer]

how would you name CCl3CHOHOH? 1-trichloro-diethanol?

[Aurelian]

how would you name CCl3CHOHOH? 1-trichloro-diethanol?

2,2,2-trichloroethanedi-1,1-ol

EDIT: Also you should write it as CCl₃CH(OH)₂ rather than "-OHOH".

[Mr Keshy]

2,2,2-trichloroethanedi-1,1-ol

EDIT: Also you should write it as CCl₃CH(OH)₂ rather than "-OHOH".

Hey quick question, would that be marked wrong in the exam?

[thushan]

2,2,2-trichloroethanedi-1,1-ol

EDIT: Also you should write it as CCl₃CH(OH)₂ rather than "-OHOH".

2,2,2-trichloroethane-1,1-diol actually

[lzxnl]

Should we say 2,2,2-trichloroethan-1,1-diol or 2,2,2-trichloroethane-1,1-diol? We normally have ethanol...without the extra e.

[Aurelian]

2,2,2-trichloroethane-1,1-diol actually

Oops, this is true

As an aside you can also put the 1,1 as a prefix (so you have 2,2,2-trichloro-1,1-ethanediol).

Should we say 2,2,2-trichloroethan-1,1-diol or 2,2,2-trichloroethane-1,1-diol? We normally have ethanol...without the extra e.

No you keep the e here =)