## HCO3-, hydrogen carbonate ion

 O3 \\ C1 = O2 / O4 \ H5
The ion charge is -1.

## Atomic Charges and Dipole Moment

C1 charge= 0.915
O2 charge=-0.803
O3 charge=-0.733
O4 charge=-0.745
H5 charge= 0.368
with a dipole moment of 1.86584 Debye

## Bond Lengths:

between C1 and O2: distance=1.268 ang___ between C1 and O3: distance=1.249 ang___
between C1 and O4: distance=1.478 ang___ between O2 and O3: distance=2.308 ang___
between O2 and O4: distance=2.290 ang___ between O3 and O4: distance=2.295 ang___
between O4 and H5: distance=0.978 ang___

## Bond Angles:

for O3-C1-O2: angle=132.8 deg___ for O4-C1-O2: angle=112.7 deg___
for H5-O4-O2: angle=69.03 deg___

## Bond Orders (Mulliken):

between C1 and O2: order=1.611___ between C1 and O3: order=1.775___
between C1 and O4: order=0.902___ between O2 and O3: order=-0.153___
between O2 and O4: order=-0.176___ between O3 and O4: order=-0.106___
between O4 and H5: order=0.877___

## Best Lewis Structure

The Lewis structure that is closest to your structure is determined. The hybridization of the atoms in this idealized Lewis structure is given in the table below. Please note that your structure can't be well described by a single Lewis structure, because of extensive delocalization.

### Hybridization in the Best Lewis Structure

1. A bonding orbital for C1-O2 with 1.9965 electrons
__has 36.01% C 1 character in a sp1.69 hybrid
__has 63.99% O 2 character in a sp1.98 hybrid

2. A bonding orbital for C1-O3 with 1.9979 electrons
__has 19.16% C 1 character in a p3 hybrid
__has 80.84% O 3 character in a p3 hybrid

3. A bonding orbital for C1-O3 with 1.9964 electrons
__has 35.95% C 1 character in a sp1.63 hybrid
__has 64.05% O 3 character in a sp1.83 hybrid

4. A bonding orbital for C1-O4 with 1.9940 electrons
__has 29.82% C 1 character in a sp2.99 hybrid
__has 70.18% O 4 character in a s0.96 p3 hybrid

5. A bonding orbital for O4-H5 with 1.9918 electrons
__has 73.13% O 4 character in a s0.83 p3 hybrid
__has 26.87% H 5 character in a s orbital

10. A lone pair orbital for O2 with 1.9752 electrons

11. A lone pair orbital for O2 with 1.8995 electrons

12. A lone pair orbital for O2 with 1.7165 electrons
__made from a p-pi orbital ( 99.89% p 0.11% d)

13. A lone pair orbital for O3 with 1.9747 electrons

14. A lone pair orbital for O3 with 1.8887 electrons

15. A lone pair orbital for O4 with 1.9886 electrons

16. A lone pair orbital for O4 with 1.9393 electrons
__made from a p-pi orbital ( 99.95% p)

99. A antibonding orbital for C1-O3 with 0.3285 electrons
__has 80.84% C 1 character in a p3 hybrid
__has 19.16% O 3 character in a p3 hybrid

101. A antibonding orbital for C1-O4 with 0.1421 electrons
__has 70.18% C 1 character in a sp2.99 hybrid
__has 29.82% O 4 character in a s0.96 p3 hybrid

-With core pairs on: C 1 O 2 O 3 O 4 -

#### Donor Acceptor Interactions in the Best Lewis Structure

The localized orbitals in your best Lewis structure can interact strongly. A filled bonding or lone pair orbital can act as a donor and an empty or filled bonding, antibonding, or lone pair orbital can act as an acceptor. These interactions can strengthen and weaken bonds. For example, a lone pair donor->antibonding acceptor orbital interaction will weaken the bond associated with the antibonding orbital. Conversly, an interaction with a bonding pair as the acceptor will strengthen the bond. Strong electron delocalization in your best Lewis structure will also show up as donor-acceptor interactions.
Interactions greater than 20 kJ/mol for bonding and lone pair orbitals are listed below.

The interaction of bonding donor orbital, 5, for O4-H5 with the second antibonding acceptor orbital, 100, for C1-O3 is 23.0 kJ/mol.

The interaction of lone pair donor orbital, 10, for O2 with the second antibonding acceptor orbital, 100, for C1-O3 is 31.2 kJ/mol.

The interaction of the second lone pair donor orbital, 11, for O2 with the second antibonding acceptor orbital, 100, for C1-O3 is 85.8 kJ/mol.

The interaction of the second lone pair donor orbital, 11, for O2 with the antibonding acceptor orbital, 101, for C1-O4 is 168. kJ/mol.

The interaction of the third lone pair donor orbital, 12, for O2 with the antibonding acceptor orbital, 99, for C1-O3 is 600. kJ/mol.

The interaction of lone pair donor orbital, 13, for O3 with the antibonding acceptor orbital, 98, for C1-O2 is 31.6 kJ/mol.

The interaction of the second lone pair donor orbital, 14, for O3 with the antibonding acceptor orbital, 98, for C1-O2 is 93.3 kJ/mol.

The interaction of the second lone pair donor orbital, 14, for O3 with the antibonding acceptor orbital, 101, for C1-O4 is 182. kJ/mol.

The interaction of lone pair donor orbital, 15, for O4 with the antibonding acceptor orbital, 98, for C1-O2 is 22.3 kJ/mol.

The interaction of the second lone pair donor orbital, 16, for O4 with the antibonding acceptor orbital, 99, for C1-O3 is 123. kJ/mol.

## Molecular Orbital Energies

The orbital energies are given in eV, where 1 eV=96.49 kJ/mol. Orbitals with very low energy are core 1s orbitals. More antibonding orbitals than you might expect are sometimes listed, because d orbitals are always included for heavy atoms and p orbitals are included for H atoms. Up spins are shown with a ^ and down spins are shown as v.

20 ----- 9.492
19 ----- 8.716

18 ----- 6.314
17 ----- 6.186

16 -^-v- 0.032

15 -^-v- -0.732

14 -^-v- -0.887

13 -^-v- -1.632

12 -^-v- -3.921

11 -^-v- -4.867
10 -^-v- -4.960

9 -^-v- -5.581

8 -^-v- -8.172

7 -^-v- -17.97

6 -^-v- -18.58

5 -^-v- -20.97

4 -^-v- -264.0

3 -^-v- -499.5
2 -^-v- -499.6

1 -^-v- -501.2

## Total Electronic Energy

The total electronic energy is a very large number, so by convention the units are given in atomic units, that is Hartrees (H). One Hartree is 2625.5 kJ/mol. The energy reference is for totally dissociated atoms. In other words, the reference state is a gas consisting of nuclei and electrons all at infinite distance from each other. The electronic energy includes all electric interactions and the kinetic energy of the electrons. This energy does not include translation, rotation, or vibration of the the molecule.

Total electronic energy = -264.5738628102 Hartrees