Resonance of HCO3^- and sigma/pi bonds

[lorka150]

Are two equivalent resonance forms HCO3^- like this?
... O
...//
O - C
...\
... O - H


...O - H
.../
O - C
...\\
...O


Both structures have brackets and a -.
Also, each O on the left has six dots, the O on the double bond has four, and the O on the H has four as well. Sorry about the ... I didn't know how else to 'draw' them so they would line up.

Are there four sigma and 1 pi?

Thanks.

 

[geoffjb]

Are two equivalent resonance forms HCO3^- like this?
... O
...//
O - C
...\
... O - H


...O - H
.../
O - C
...\\
...O


Both structures have brackets and a -.
Also, each O on the left has six dots, the O on the double bond has four, and the O on the H has four as well. Sorry about the ... I didn't know how else to 'draw' them so they would line up.

Are there four sigma and 1 pi?

Thanks.

The two structures you have drawn are not resonance structures. You have simply rotated the molecule 180 degrees along the horizontal axis. Try to remember that, when drawing resonance structures, only electrons can move (not atoms).

 

[lorka150]

Thanks Geoff... In that case, I'm quite confused.

 

[geoffjb]

Thanks Geoff... In that case, I'm quite confused.

Keep the molecule oriented the same in all resonance structures. In other words, the H must stay on the same O.

What level of chemistry is this question from? Are you required to list only major resonance structures, or all of them?

 

[lorka150]

Thanks for the help so far, Geoff. I am only supposed to list two equivalent (I assume that might be the key word there) resonance forms.
it's from first year university chemistry - just very out of my element.

... O
...//
O - C
...\
... O - H


...O
.../
O - C
...\\
...O -H

Is that what you are indicating?

 

[geoffjb]

Thanks for the help so far, Geoff. I am only supposed to list two equivalent (I assume that might be the key word there) resonance forms.
it's from first year university chemistry - just very out of my element.

... O
...//
O - C
...\
... O - H...O
.../
O - C
...\\
...O -H

Is that what you are indicating?

Although these are resonance structures, they are certainly not equivalent.

Why do you think the double bond will shift to the O with an H attached?

 

[geoffjb]

Thanks for the help so far, Geoff. I am only supposed to list two equivalent (I assume that might be the key word there) resonance forms.
it's from first year university chemistry - just very out of my element.

... O
...//
O - C
...\
... O - H...O
.../
O - C
...\\
...O -H

Is that what you are indicating?

Try rotating the molecule so that the alcohol is pointing to the left.

     O
    //
H-O-C
     \
      O

Give the equivalent resonance structure of the molecule. I'll assume you can see it now.