Do you know the Lewis Structure of these molecules?

Question

BrCN, SOCl2 (OSCl2). CH3NH2, (CH3)2O, N2H2(HNNH)

Please give a short explanation!

Answer 1

Agreed with previous answerer, except...

SOCl2 has an S=O double bond rather than single bond.

Answer 2

Br -C///N  

Where /// is a triple bond

SOCl2 or OSCl2

A formal charge analysis suggests that S should be in the middle.  All single bonds.  Oxygen has an octet, and S has a lone pair

H3C-N-H2  

All single bonds.  Lone pair on N.

H3C-O-CH3

All single bonds. Two lone pairs on O

H2N-NH2

All single bonds.  A lone pair on each of the N's

========= Follow up =========

Contrary to popular opinion, there's pretty good evidence that the bond between S and O is not a double bond.  (Not a full double bond, anyway.  More on that later.)   A simplistic analysis basically comes down to VSEPR theory vs formal charge.  (We'll get to MO theory in a moment.)

VSEPR theory would predict all single bonds where the elements all follow the "octet rule".  There is no reason to make a double bond between S and O.  There are 26 valence electrons to distribute, and each atom gets an octet.  

Then we get to formal charge.  With all single bonds the formal charge on oxygen is -1 and on sulfur it is +1.  That's fine.  The more electronegative element gets the negative formal charge.  But if we place a double bond between O and S and violate the octet rule by forcing S to have "five bonds", an expanded octet, then the formal charges can be reduced to zero.  

But this places too much importance on the concept of formal charge.  Remember, formal charge does not indicate an ACTUAL charge.  It is only a mathematical "trick" to help in determining the best ARRANGEMENT of atoms, NOT the best distribution of ELECTRONS.

So the octet rule says all single bonds.  The "over use" of formal charge says to put a double bond between S and O.  The best descriptor of the molecule comes from molecular orbital theory, and one way to do that is through computational chemistry.

So a computational chemistry run of OSCl2 actually comes up with a bond order of not quite 1.5 for the bond between S and O.  Now, there's a nice happy medium.  But it also describes three lone pairs for oxygen, which you can't do with  VSEPR theory and a double bond between S and O.

Check out the run at http://www.colby.edu/chemistry/webmo/SOC...