Ethane's structure showcases the beauty of carbon bonding. Two methyl groups join hands through a single C-C bond, with each carbon sporting a tetrahedral arrangement of sp3 hybrid orbitals. This setup allows for strong, directional covalent bonds and that iconic 109.5° angle.
Diving into the bonds, we see C-H connections outshining their C-C counterparts. These shorter, stronger links result from hydrogen's small size and the electronegativity difference. Meanwhile, the C-C bond's symmetry enables free rotation, a key feature in ethane's flexibility.
Structure and Bonding in Ethane
Structure of ethane molecule
- Ethane ($CH_3CH_3$) composed of two methyl groups joined by a single C-C bond
- Each carbon atom undergoes sp3 hybridization combines one 2s and three 2p orbitals forming four equivalent sp3 hybrid orbitals
- sp3 hybrid orbitals arrange in a tetrahedral geometry surrounding each carbon atom minimizing electron repulsion and maximizing stability
- C-C bond formed by overlap of one sp3 hybrid orbital from each carbon atom creates a sigma ($\sigma$) bond (single bond)
- Remaining three sp3 hybrid orbitals on each carbon atom overlap with 1s orbitals of hydrogen atoms forming C-H sigma ($\sigma$) bonds
- Bond angles in ethane approximately 109.5° result from tetrahedral arrangement of sp3 hybrid orbitals around each carbon atom (tetrahedral geometry)
Carbon-carbon bonding with sp3 orbitals
- In ethane and saturated hydrocarbons carbon atoms form single bonds using sp3 hybrid orbitals
- sp3 hybridization process mixes one 2s and three 2p atomic orbitals creating four equivalent sp3 hybrid orbitals
- sp3 hybrid orbitals orient in a tetrahedral arrangement minimizing electron repulsion and maximizing stability (staggered conformation)
- C-C bond forms through end-on overlap of one sp3 hybrid orbital from each carbon atom creates a sigma ($\sigma$) bond (strong covalent bond)
- Remaining sp3 hybrid orbitals on each carbon atom can form additional single bonds with other atoms (hydrogen, carbon)
- Orbital overlap between sp3 hybrid orbitals results in strong, directional covalent bonds
C-H vs C-C bonds in ethane
- In ethane C-H and C-C bonds are sigma ($\sigma$) bonds formed by overlap of atomic orbitals
- C-H bonds:
- Formed by overlap of sp3 hybrid orbital from carbon and 1s orbital from hydrogen
- Bond length approximately 1.09 Å (angstroms) shorter than C-C bond
- Bond energy approximately 99 kcal/mol stronger than C-C bond
- C-C bond:
- Formed by overlap of two sp3 hybrid orbitals one from each carbon atom
- Bond length approximately 1.54 Å (angstroms) longer than C-H bond
- Bond energy approximately 83 kcal/mol weaker than C-H bond
- C-H bond shorter and stronger than C-C bond due to:
- Smaller size of hydrogen atom compared to carbon atom leads to shorter bond length
- Greater electronegativity difference between carbon and hydrogen leads to more polar and stronger bond (dipole moment)
Hybridization and Bonding in Ethane
- Electron configuration of carbon (1s² 2s² 2p²) undergoes hybridization to form sp3 hybrid orbitals
- Hybridization results in four equivalent sp3 hybrid orbitals used in bonding
- Bond rotation around the C-C single bond in ethane is possible due to the symmetrical nature of the sigma (σ) bond