## HCCH, Acetylene

 H3 - C1 E C2 - H4
Tell me about the atomic charges, dipole moment, bond lengths, angles, bond orders,
molecular orbital energies, or total energy.
Tell me about the best Lewis structure.

## Atomic Charges and Dipole Moment

C1 charge=-0.282
C2 charge=-0.284
H3 charge= 0.283
H4 charge= 0.283
with a dipole moment of 0 Debye

## Bond Lengths:

between C1 and C2: distance=1.213 ang___ between C1 and H3: distance=1.074 ang___
between C2 and H4: distance=1.074 ang___

## Bond Angles:

for H3-C1-C2: angle=179.9 deg___ for H4-C2-C1: angle=179.9 deg___

## Bond Orders (Mulliken):

between C1 and C2: order=2.931___ between C1 and H3: order=0.947___
between C2 and H4: order=0.947___

## 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.

### Hybridization in the Best Lewis Structure

1. A bonding orbital for C1-C2 with 1.9998 electrons
__has 50.00% C 1 character in a p-pi orbital ( 99.82% p 0.18% d)
__has 50.00% C 2 character in a p-pi orbital ( 99.82% p 0.18% d)

2. A bonding orbital for C1-C2 with 1.9998 electrons
__has 50.00% C 1 character in a p-pi orbital ( 99.82% p 0.18% d)
__has 50.00% C 2 character in a p-pi orbital ( 99.82% p 0.18% d)

3. A bonding orbital for C1-C2 with 1.9919 electrons
__has 50.00% C 1 character in a sp0.92 hybrid
__has 50.00% C 2 character in a sp0.92 hybrid

4. A bonding orbital for C1-H3 with 1.9890 electrons
__has 61.82% C 1 character in a sp1.08 hybrid
__has 38.18% H 3 character in a s orbital

5. A bonding orbital for C2-H4 with 1.9890 electrons
__has 61.82% C 2 character in a sp1.08 hybrid
__has 38.18% H 4 character in a s orbital

-With core pairs on: C 1 C 2 -

#### 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, 4, for C1-H3 with the third antibonding acceptor orbital, 58, for C1-C2 is 29.7 kJ/mol.

The interaction of bonding donor orbital, 5, for C2-H4 with the third antibonding acceptor orbital, 58, for C1-C2 is 29.7 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.

11 ----- 2.747

10 ----- 1.517

9 ----- -0.544 8 ----- -0.544

7 -^-v- -7.289 6 -^-v- -7.291

5 -^-v- -12.21

4 -^-v- -13.95

3 -^-v- -18.46

2 -^-v- -266.6
1 -^-v- -266.7

## 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 = -77.3520742511 Hartrees