How Do You Draw Correct Resonance Structures for H3CHCHC=NH?

  • Thread starter Thread starter rmiller70015
  • Start date Start date
  • Tags Tags
    Resonance
Click For Summary
SUMMARY

The discussion centers on drawing correct resonance structures for the anion H3CHCHC=NH. The participant initially miscalculated the valence electrons, arriving at 24 instead of the correct distribution. The correct resonance structure involves a double bond between carbons 2 and 3, with nitrogen carrying two lone pairs and a -1 charge. The major resonance form is the one with the double bond between carbon 2 and carbon 3, while the less stable form shows the charge distribution incorrectly.

PREREQUISITES
  • Understanding of Lewis Structures
  • Knowledge of valence electrons and their distribution
  • Familiarity with resonance structures in organic chemistry
  • Basic concepts of anions and charge distribution
NEXT STEPS
  • Study the principles of resonance in organic molecules
  • Learn how to calculate and distribute valence electrons accurately
  • Explore the significance of major and minor resonance forms
  • Review the rules for drawing Lewis Structures for complex organic compounds
USEFUL FOR

Chemistry students, particularly those studying organic chemistry, educators teaching resonance concepts, and anyone interested in mastering Lewis Structures and resonance forms.

rmiller70015
Messages
110
Reaction score
1

Homework Statement


This is a problem with Sappling involved. I was given a Lewis Structure, told it was an anion (no charges were given just that it was one) and told to fix the structure and draw a resonance.

Homework Equations


No Equations.

The Attempt at a Solution


The problem starts out with the basic structure, there is a double bond between the carbon and the nitrogen, no charges and no lone pairs on the structure.

I counted up the number of valance electrons for this structure and got 23e-, since it's an anion, I added 1 extra electron (note they did not say the charge on the anion just that it was one). Now I have a total of 24 valence electrons in the molecule. The bonds take up 20 e- and that leaves 4 e- left over. I distributed a pair to the Carbon with 3 bonds (the first CH, or Carbon-2) and to the Nitrogen. This makes the Nitrogen neutral and gives the 2 carbon a -1 charge and the entire molecule has a -1 charge, an anion. But this is incorrect according to Sappling and I can't figure out another way to arrange the electrons so that the molecule makes sense.

As for the Resonance I pushed the electrons I had placed on the first model into different positions, putting a double bond between carbons 2 and 3 and a single bond between carbon 3 and the nitrogen. Also I gave the nitrogen 2 sets of lone pairs and a -1 charge. This resonance is correct according to sappling, but the initial model I amended is not.

I know it's not recommended to post a picture on here, but I'm drawing models and I don't see any other way to accurately describe what I have done, than to post a picture of my drawing so here it is:
http://imgur.com/6U0x4CI
 
Physics news on Phys.org
The 'original' drawing is missing a hydrogen atom, of course, which you added later.
"Resonance" is the character of having TWO significant resonance forms - forms in which the atoms are in the same place, but the charges are not. The actual structure has the charge distribution as a mixture of the two forms with their localized charges.
The major (most stable) resonance form is the one you show as "resonance" in your drawing; a less stable resonance form is the one labeled "my changes".
The proper way to show this (my opinion as practicing chemist) is to write the two forms with a double-headed arrow between them, showing that both contribute. In this case, most of the charge will be on the Nitrogen atom, much less on the Carbon atom
 
  • Like
Likes rmiller70015

Similar threads

  • · Replies 9 ·
Replies
9
Views
10K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 1 ·
Replies
1
Views
6K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 7 ·
Replies
7
Views
4K
  • · Replies 4 ·
Replies
4
Views
7K