| 1.15 Bonding in Methane and Orbital Hybridization |
| Structure of Methane |
| tetrahedral | |
| bond angles = 109.5� | |
| bond distances = 110 pm | |
| but structure seems inconsistent
with electron configuration of carbon |
| Electron configuration of carbon |
| only two unpaired electrons |
|
| should form s bonds to only two hydrogen atoms |
|
| bonds should be at right angles to one another |
| sp3 Orbital Hybridization |
| Promote an electron from the 2s to the 2p orbital |
| sp3 Orbital Hybridization |
| sp3 Orbital Hybridization |
| Mix together (hybridize) the 2s orbital and the three 2p orbitals |
| sp3 Orbital Hybridization |
| 4 equivalent half-filled orbitals are consistent with four bonds and tetrahedral geometry |
| Shapes of orbitals |
| Nodal properties of orbitals |
| Shape of sp3 hybrid orbitals |
| take the s orbital and place it on top of the p orbital |
| Shape of sp3 hybrid orbitals |
| reinforcement of electron wave in regions where sign is the same | |
| destructive interference in regions of opposite sign |
| Shape of sp3 hybrid orbitals |
| orbital shown is sp hybrid | |
| analogous procedure using three s orbitals and one p orbital gives sp3 hybrid | |
| shape of sp3 hybrid is similar |
| Shape of sp3 hybrid orbitals |
| hybrid orbital is not symmetrical | |
| higher probability of finding an electron on one side of the nucleus than the other | |
| leads to stronger bonds |
| Slide 14 |
| "consistent with structure of methane" |
| consistent with structure of methane | |
| allows for formation of 4 bonds rather than 2 | |
| bonds involving sp3 hybrid
orbitals are stronger than those involving s-s overlap or p-p overlap |
| 1.16 sp3 Hybridization and Bonding in Ethane |
| "tetrahedral geometry at each carbon" |
| tetrahedral geometry at each carbon | |
| C�H bond distance = 110 pm | |
| C�C bond distance = 153 pm |
| "In-phase overlap of half..." |
| In-phase overlap of half-filled sp3
hybrid orbital of one carbon with half-filled sp3 hybrid orbital of another. |
|
| Overlap is along internuclear axis to give a s bond. |
| "In-phase overlap of half..." |
| In-phase overlap of half-filled sp3
hybrid orbital of one carbon with half-filled sp3 hybrid orbital of another. |
|
| Overlap is along internuclear axis to give a s bond. |
| 1.17 sp2 Hybridization and Bonding in Ethylene |
| Structure of Ethylene |
| planar | |
| bond angles: close to 120� | |
| bond distances: C�H = 110 pm C=C = 134 pm |
| sp2 Orbital Hybridization |
| Promote an electron from the 2s to the 2p orbital |
| sp2 Orbital Hybridization |
| sp2 Orbital Hybridization |
| Mix together (hybridize) the 2s orbital and two of the three 2p orbitals |
| sp2 Orbital Hybridization |
| 3 equivalent half-filled sp2 hybrid orbitals plus 1 p orbital left unhybridized |
| sp2 Orbital Hybridization |
| sp2 Orbital Hybridization |
| p Bonding in Ethylene |
| p Bonding in Ethylene |
| each carbon has an unhybridized 2p
orbital axis of orbital is perpendicular to the plane of the s bonds |
| p Bonding in Ethylene |
| side-by-side overlap of
half-filled p orbitals gives a p bond |
|
| double bond in ethylene has a s component and a p component |
| 1.18 sp Hybridization and Bonding in Acetylene |
| Structure of Acetylene |
| linear | |
| bond angles: 180� | |
| bond distances: C�H = 106 pm CC = 120 pm |
| sp Orbital Hybridization |
| Promote an electron from the 2s to the 2p orbital |
| sp Orbital Hybridization |
| sp Orbital Hybridization |
| Mix together (hybridize) the 2s orbital and one of the three 2p orbitals |
| sp Orbital Hybridization |
| 2 equivalent half-filled sp hybrid orbitals plus 2 p orbitals left unhybridized |
| sp Orbital Hybridization |
| sp Orbital Hybridization |
| p Bonding in Acetylene |
| p Bonding in Acetylene |
| one p bond involves one of the p orbitals on each carbon | |
| there is a second p bond perpendicular to this one |
| p Bonding in Acetylene |
| p Bonding in Acetylene |
| 1.19 Which Theory of Chemical Bonding is Best? |
| Three Models |
| Lewis | |
| most familiar�easiest to apply | |
| Valence-Bond (Orbital Hybridization) | |
| provides more insight than Lewis model | |
| ability to connect structure and reactivity to hybridization develops with practice | |
| Molecular Orbital | |
| potentially the most powerful method | |
| but is the most abstract | |
| requires the most experience to use effectively |