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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: sun725 on December 15, 2016, 01:58:54 PM

Title: Resonance structure
Post by: sun725 on December 15, 2016, 01:58:54 PM

I want to draw the resonance structure of the following drug
https://pubchem.ncbi.nlm.nih.gov/image/imgsrv.fcgi?cid=33741&t=l

I only came up with one resonance structure that it's able to make at the ether group. Is that correct, or is it possible to make more? And what's the importance of this resonance for the electron configuration? I think that it increases the stability by increasing the bonding between adjacent atoms. However, I have a hard time relating it to this example...

Thanks in advance.

Title: Re: Resonance structure
Post by: AWK on December 15, 2016, 02:34:33 PM

Let's try.
Could you draw resonance structures for phenol or anisol?

Title: Re: Resonance structure
Post by: sun725 on December 15, 2016, 04:30:55 PM

Okay, I tried with Phenol. Excuse my bad handwriting...
http://imgur.com/a/hpDbh

Title: Re: Resonance structure
Post by: AWK on December 15, 2016, 04:43:23 PM

In resonance structure you cannot move or remove any atom. You can move only electron pairs (or single electron in the case of radicals). You lost 1 hydrogen atom.

Title: Re: Resonance structure
Post by: sun725 on December 15, 2016, 04:52:20 PM

Yes, I see that now ...
I'll try to show you what I came up with the other molecule that I posted earlier. However, I only drew 1 structure ...

Title: Re: Resonance structure
Post by: sun725 on December 15, 2016, 05:30:15 PM

My attempt ...
http://imgur.com/a/EbR5Q

Title: Re: Resonance structure
Post by: Babcock_Hall on December 15, 2016, 05:33:20 PM

In general the combination of resonance structures gives a better picture of where the electron density is than any single structure that we could draw.  I would not say that it necessarily increases the number of bonds between two atoms.  However for any particular example, the number of bonds between two atoms is usually different from one resonance structure to the next.

Title: Re: Resonance structure
Post by: AWK on December 15, 2016, 06:11:20 PM

Oxygen atom in phenol or phenyl methyl ether in mesomeric structures cannot bear negative charge. It is against Lewis theory.

Title: Re: Resonance structure
Post by: sun725 on December 16, 2016, 11:06:02 AM

Yes, I made that mistake. Tried to correct it and came up with something hopefully a little more correct??

Title: Re: Resonance structure
Post by: sun725 on December 16, 2016, 11:08:13 AM

http://imgur.com/a/e78Nj

Title: Re: Resonance structure
Post by: AWK on December 16, 2016, 03:37:58 PM

One more resonance structure is needed. Then relocate these findings to your structure.

Title: Re: Resonance structure
Post by: sun725 on December 16, 2016, 07:11:43 PM

Okay,
http://imgur.com/a/gJ2yu

Hoping I got it somehow right now..

Title: Re: Resonance structure
Post by: AWK on December 17, 2016, 12:53:50 AM

Are you sure that carbon atom can be pentavalent?

Title: Re: Resonance structure
Post by: sun725 on December 17, 2016, 06:15:05 AM

Okay, that's a huge mistake. That's not possible ...
Feeling very stupid, but that's what I think it should be now...
http://imgur.com/a/x66f4

Title: Re: Resonance structure
Post by: AWK on December 17, 2016, 08:46:17 AM

On the last structure + and - are missing. Now find on the molecule of tramadol this part which looks like to anisole and draw resonance structures of this pain medication.

Title: Re: Resonance structure
Post by: sun725 on December 17, 2016, 11:58:34 AM

Okay, I think I got it now:
http://imgur.com/a/kIOuD

However, what does that mean for the electron configuration? Does it make the molecule more stable that it's able to make these resonance structures? Can you please explain this part?

I really appreciate the help I get here.

Title: Re: Resonance structure
Post by: AWK on December 17, 2016, 02:09:27 PM

Resonance structures organic chemists use for predicting chemical reactivity of aromatic molecues.

Title: Re: Resonance structure
Post by: sun725 on December 17, 2016, 02:12:17 PM

Okay. But how can I relate it to this certain molecule? And are the structures correct now?

Title: Re: Resonance structure
Post by: AWK on December 17, 2016, 02:24:59 PM

resonance structures for anisole are correct.