Conversation started Jan 19, 2017 at 16:11.
hBy2Py
hBy2Py
Jan 19, 2017 16:11
@DHMO I ran a quick ORCA optimization on HCO+:

! RKS PBE0 def2-SVP def2-SVP/J RIJCOSX
! GRID4 GRIDX5 TIGHTOPT ANFREQ
! PRINTBASIS

* xyzfile 1 1 HCO_p.xyz
Then ran the resulting wavefunction through a QTAIM analysis in MultiWFN
The AIM charges I get are:

H +0.51
C +1.43
O –0.94
DHMO
DHMO
That's interesting
hBy2Py
hBy2Py
The ELF basins show:

C-H bond : 2.21e (~single)
C-O bond : 3.91e (~double)
O LPs : 3.66e (slightly deficient value for two lone pairs)
C core : 2.09e (carbon 1s electrons, typical value)
O core : 2.13e (oxygen 1s electrons, typical value)
DHMO
DHMO
@hBy2Py could you run your programs for CO?
hBy2Py
hBy2Py
Sure, I think I even have that already optimized somewhere...
Back on HCO+ briefly, the H-C bond is a standard covalent bond, but the C-O bond is somewhere between a charge-shift bond and a dative / coordinate covalent bond
Mmmm... the C-O bond in CO is very similar to the C-O bond in HCO+
Which is logical, HCO+ may just be protonated CO
DHMO
DHMO
but the O is supposed to be positive... @hBy2Py
Ramanujan
Ramanujan
Jan 19, 2017 16:25
Hi
hBy2Py
hBy2Py
Hello
Chemobot
Chemobot
edited !
hBy2Py
hBy2Py
@DHMO That may be, but QTAIM at least doesn't see it that way.
C +1.2
O -1.2
Ramanujan
Ramanujan
$H^+$ and $H_3 O^+$ are same?
hBy2Py
hBy2Py
@Ramanujan Not strictly, but for most purposes, yes, when looking at acids in aqueous solution.
DHMO
DHMO
Jan 19, 2017 16:27
yes
@hBy2Py hmm...
hBy2Py
hBy2Py
vamoose
DHMO
DHMO
do you have any MO-related software?
Ramanujan
Ramanujan
In what sense they are same? Both have positive Oxidation state but one is only Hydrogen and other has one oxygen and 3 hydrogen
DHMO
DHMO
@Ramanujan you can view $\ce{H3O+}$ as $\ce{H+}$ attached to $\ce{H2O}$.
Ramanujan
Ramanujan
@DHMO attached to means X_{aq} ?
DHMO
DHMO
Jan 19, 2017 16:32
attached to means bonded with
Ramanujan
Ramanujan
Ok
hBy2Py
hBy2Py
Jan 19, 2017 17:14
@DHMO Bear in mind, these charges have little to do with the dipole.
DHMO
DHMO
@hBy2Py why?
hBy2Py
hBy2Py
An appreciable fraction of the electron density on the carbon side of the bond plane is associated with the oxygen atom.
It's due to the way AIM defines the atom boundaries
For CO, the ORCA computation puts the dipole at 0.128 Debye, oxygen positive
DHMO
DHMO
for HCO?
hBy2Py
hBy2Py
For HCO+, it puts it at 4.04 Debye, oxygen negative
DHMO
DHMO
that's a large dipole
hBy2Py
hBy2Py
Jan 19, 2017 17:20
For sure
Protonation has a remarkably significant effect on the electron density distribution.
The proton basically acts as a localization center, IIUC
In the case of HCO+, it appears that it localizes electrons away from itself.
Related -- with CO, often it's written as a triple bond
But the AIM ELF basin populations don't support that:
C LP - 2.49e (Slightly over one lone pair on C)
C-O bond - 3.07e (~1.5-order bond)
O LPs - 4.23e (~two lone pairs)
Again, that C-O bond in CO looks to have appreciable charge-shift bond character. High-level, that means that electron density gets "smooshed" out from the bonding region and (often) into the lone-pair region of the atoms involved.
Much of the smooshed density appears to end up on carbon, with a tad going onto the oxygen.
DHMO
DHMO
so what is the conclusion? @hBy2Py
hBy2Py
hBy2Py
CO has a double bond with charge shift character
HCO+ is likely protonated CO, also with a C=O double bond, with some charge shift character but overall less than with CO
Protonation of CO appears to change the direction of the dipole moment rather dramatically
@DHMO Not sure if there's any particular connection back to the mass spectrum of formic acid
DHMO
DHMO
Jan 19, 2017 17:35
is it particularly stable?
hBy2Py
hBy2Py
¯\_(ツ)_/¯
I can't tell that from the quick analyses I've done thus far.
 
Conversation ended Jan 19, 2017 at 17:36.