[lrisNil]

Butanal is on the right and I was wondering how do you draw the resonance structures for it?

These are my attempts so far:

1. It's not shown but I think the O has 2 lone pairs. But they can't move because that would make a triple bond, so  I don't think I can push electrons that direction.

2. Another thing I thought was to push the double bond to the right (not to the H because I don't think H can have double bonds.) If I do this, is this a correct resonance structure?

Then the O would get the symbol + because it lost the double bond I think, but I'm not sure if this is correct!
And where would the - symbol go?  on the Carbon connected with the O or the carbon connected with another carbon?

thank you for reading this

[Ben Bob2]

1. It's not shown but I think the O has 2 lone pairs. But they can't move because that would make a triple bond, so  I don't think I can push electrons that direction.

Correct; the resulting structure would not follow the octet rule because the carboxyl carbon would have too many electrons. This is not a resonance structure.

2. Another thing I thought was to push the double bond to the right (not to the H because I don't think H can have double bonds.) If I do this, is this a correct resonance structure?

Nope, this would be wrong as well because the carbon atom would then have five bonds.
The resonance structure must be a valid Lewis structure as well, meaning that hydrogen can't have more than two electrons and carbon or oxygen can't have more than eight.

That leaves one valid option: think about the one other place that two of the double-bonded electrons could go. Hint: oxygen would become negative

[lrisNil]

1. Thank you! So if  push the electrons to the left, they land on the Oxygen. Does this mean this is the only resonance structure? Since I can't find any other places the electrons could go. 

2. Also, for the structure on the left, does it have a similar dipole moment where you can only push the electrons to the Oxygen?

[Demosthenes]

Hello Iris,

Working on the assignment for Chem 282? Me too 

Sounds like you've got butanal down. The trans butenal's oxygen can also have the electrons pushed onto it, but it also has that extra double bond whose electrons could probably go somewhere though (hint hint  )

[lrisNil]

Hello Iris,

Working on the assignment for Chem 282? Me too 

Sounds like you've got butanal down. The trans butenal's oxygen can also have the electrons pushed onto it, but it also has that extra double bond whose electrons could probably go somewhere though (hint hint  )

Thank you so much! I Drew 2 resonance structures for Trans-2-butenal. Do you have any ideas for the reasoning why more resonance structures means higher dipole moment?