August 04, 2024, 04:20:42 PM
Forum Rules: Read This Before Posting

0 Members and 1 Guest are viewing this topic.

#### zhouduck

• New Member
• Posts: 8
• Mole Snacks: +0/-0
« on: June 26, 2010, 02:13:37 AM »
When naming Enantiomers as s(left) or r(right), we need to assign the priority of the atoms directly attached to the chirality center.

If 2+ groups have the same atom, look at the next set of atoms until a point of difference is found.

If the first set of atoms which are directly attached to the chirality center are C(1), C(2), C(3) and H. Then we assign H the lowest priority d. The three atoms attached to C(1) are H, H and H; the three atoms attached to C(2) are Br, H, and H; the three atoms attached to C(3) are Cl, Cl, and Cl. Then, we assign C(1) the second lowest priority c. but about C(2) and C(3), who has higher priority? C(2) or C(3)?

Groups with multiple bonds are treated as if both atoms were doubled or tripled.

If the first set of atoms which are directly attached to the chirality center are C(1), C(2), C(3) and H. Then we assign H the lowest priority d. The three atoms attached to C(1) are H, H and H; the two groups attached to C(2) are CH2 with a double bond, and a CH3 with a single bond; the only group attached to C(3) is CH with a triple bond. Then, we assign C(1) the second lowest priority c. but about C(2) and C(3), who has higher priority? C(2) or C(3)?

Anyone? Thanks!!!!!!

#### nj_bartel

• Sr. Member
• Posts: 1487
• Mole Snacks: +76/-42
##### Re: Question about Enantiomer Nomenclature
« Reply #1 on: June 26, 2010, 04:08:31 AM »
first one: 2 - it has a bromine attached, which is a higher MW than hydrogen.

second one: Hmm.  I'd have to say 2, since you have substituents beyond what 3 has (while the other ones are equal).  Not positive though.

#### zhouduck

• New Member
• Posts: 8
• Mole Snacks: +0/-0
##### Re: Question about Enantiomer Nomenclature
« Reply #2 on: June 26, 2010, 04:29:19 AM »
Hi Nj,
I checked with the solution and it says the one with the triple bond has the highest priority. I've posted the picture from the slide