Can anyone tell me why Carbon #5 is not chiral?

[matth87]

---

Members do not see this ad.

hi can anyone tell me why carbon #5 is not chiral?

 

[pOrtEnt]

carbon five is sp2 hybridized; therefore it is planar and cannot be chiral.

 

[matth87]

Omg im a ******....

I forgot that stupid circle was a double bond.. was thinking there was a hydrogen there for some reason...

 

[MCATBear]

it's a little confusing to see with the circle in the benzene instead of drawing double bonds, but because the carbon 5 has a double bond to another carbon, it's sp2 and can't be chiral.

 

[Seraph 84]

Haha, I thought it was chiral too when I looked at it, guess I better start on organic!

 

[capostat]

another question, because I see this with ring structures and it confuses me...

what if there was no pi-bond system in the ring and no Nitrogen there either?

Carbon 5--it has a substituent matched on either side as you go around the ring... like nobody wins for priority 2 and 3. But i could swear that I've seen it still considered chiral. no?

 

[matth87]

another question, because I see this with ring structures and it confuses me...

what if there was no pi-bond system in the ring and no Nitrogen there either?

Carbon 5--it has a substituent matched on either side as you go around the ring... like nobody wins for priority 2 and 3. But i could swear that I've seen it still considered chiral. no?

No that wouldn't be considered chiral because if they match on both sides then the substituent groups would not be different.

Chiral molecules must have 4 different substituent groups

 

[capostat]

No that wouldn't be considered chiral because if they match on both sides then the substituent groups would not be different.

Chiral molecules must have 4 different substituent groups

alright, good to know...i may have missed a different group or something.

BUT i've seen a thread where that C5 would instead be labeled a STEREOGENIC center.

 

[loveoforganic]

Stereogenic means stereochemistry can arise from that site, which is true. Hydrogenation of the ring for example.

 

[capostat]

Stereogenic means stereochemistry can arise from that site, which is true. Hydrogenation of the ring for example.

ok i now know what that term implies...thanks.

did you mean halogenation by the way?

 

[loveoforganic]

I meant what I said 😛

 

[capostat]

I meant what I said 😛

ok i was thinking that hydrogenation for the entire ring would just eliminate all the units of saturation without making it chiral. halogenation all over the ring would do that too i guess.

anyway, 4 uniques--chiral.

 

[loveoforganic]

You have to get rid of the double bonds. Halogenation doesn't do that.

 

[0Complications]

Also, don't confuse sterogenic with a stereocenter.


Stereocenter = Chiral

 

[capostat]

gotcha X 2...

 

[rgpetschek]

hi can anyone tell me why carbon #5 is not chiral?

This molecule is not planar. The ring with carbon 5 in it is (more or less) perpendicular to the ring with carbon 4 in it Because of the nitrogens in each of the rings there is no mirror plane that, in any specific configuration will take the molecule into itself. However, the rings can rotate relative to each other around the bond between carbons 4 and 5 so that while each likely configuration of the molecule is chiral, the molecule "forgets" its chirality so quickly (microseconds at most at room temperature that the molecule is not usually referred to as chiral. However, if there were more "stuff" attached to the rings (attached e.g. to the carbons that are bounded to carbons 4 and 5) then the rings can not rotate quickly relative to each other, and the molecule is chiral (and could be even if all bonds where sp2. But, these kinds of molecules (while known from synthetic chemistry) are far less common in biology. In fact, I know of none that are naturally occurring.

 

[orthomyxo]

Fooled me. God I suck at orgo.