Constitution of Organic Compounds
The ELECTRONIC STRUCTURE of the atoms within an organic molecule determines its 3D arrangement and its properties.
FOUR ELECTRON DENSITIES
Just as four balloons tied together point towards the vertices of a tetrahedron, four electron densities adopt this arrangement in order to be as far apart from each other as possible and thus minimize their repulsion.
CARBON
The shapes of the s and p atomic orbitals do not allow us to explain the geometry of a TETRAHEDRAL carbon. That is why we need to transform (HYBRIDIZE) those orbitals into four new orbitals with a TETRAHEDRAL geometry. The new HYBRID ORBITALS are called sp3 because they arise from one s and three p orbitals of carbon.
Practise with molecules containing carbons bonded to four atoms. What geometry do the atoms display?
NITROGEN
The shapes of the s and p atomic orbitals do not allow us to explain the geometry of a PYRAMIDAL nitrogen. That is why we need to transform (HYBRIDIZE) those orbitals into four new orbitals with a TETRAHEDRAL geometry. The new HYBRID ORBITALS are called sp3 because they arise from one s and three p orbitals of nitrogen.
One of the four sp3 hybrid orbitals of nitrogen does not form a bond but holds what is called a lone electron pair. Therefore, the geometry of the nitrogen and its three bonded atoms is PYRAMIDAL, although the four orbitals keep a TETRAHEDRAL geometry.
Practise with molecules containing carbons bonded to four atoms and nitrogens bonded to three. What geometry do the atoms display?
OXYGEN
The shapes of the s and p atomic orbitals do not allow us to explain the geometry of an ANGULAR oxygen. That is why we need to transform (HYBRIDIZE) those orbitals into four new orbitals with a TETRAHEDRAL geometry. The new HYBRID ORBITALS are called sp3 because they arise from one s and three p orbitals of oxygen. Two of the four sp3 hybrid orbitals of oxygen do not form bonds, and each holds what is called a lone electron pair. Therefore, the geometry of the oxygen and its two bonded atoms is ANGULAR, although the four orbitals keep a TETRAHEDRAL geometry.
Practise with molecules containing carbons bonded to four atoms and oxygens bonded to two. What geometry do the atoms display?
THREE ELECTRON DENSITIES
Just as three balloons tied together point towards the vertices of a triangle, three electron densities adopt this arrangement in order to be as far apart from each other as possible and thus minimize their repulsion.
CARBON
The shapes of the s and p atomic orbitals do not allow us to explain the geometry of a TRIGONAL PLANAR carbon either. That is why we need to transform (HYBRIDIZE) those orbitals into three new orbitals with a TRIGONAL PLANAR geometry. The new HYBRID ORBITALS are called sp2 because they arise from one s and two p orbitals of carbon. One p orbital is left over on each carbon, which explains the 'double bond'.
Practise with molecules containing carbons bonded to three atoms. What geometry do the atoms display?
NITROGEN
The shapes of the s and p atomic orbitals do not allow us to explain the geometry of an ANGULAR nitrogen either. That is why we need to transform (HYBRIDIZE) those orbitals into three new orbitals with a TRIGONAL PLANAR geometry. The new HYBRID ORBITALS are called sp2 because they arise from one s and two p orbitals of nitrogen.
One of the three sp2 hybrid orbitals of nitrogen does not form a bond but holds what is called a lone electron pair. Therefore, the geometry of the nitrogen and its two bonded atoms is ANGULAR, although the three orbitals keep a TRIGONAL PLANAR geometry.
One p orbital is left over on the carbon and another on the nitrogen, which explains the 'double bond'.
Practise with molecules containing carbons bonded to several atoms and nitrogens bonded to two. What geometry do the atoms display?
OXYGEN
The shapes of the s and p atomic orbitals do not allow us to explain the geometry of a double-bonded oxygen either. That is why we need to transform (HYBRIDIZE) those orbitals into three new orbitals with a TRIGONAL PLANAR geometry. The new HYBRID ORBITALS are called sp2 because they arise from one s and two p orbitals of oxygen.
Two of the three sp2 hybrid orbitals of oxygen do not form bonds, and each holds what is called a lone electron pair.
One p orbital is left over on the carbon and another on the oxygen, which explains the 'double bond'.
Practise with molecules containing carbons bonded to several atoms and oxygens bonded to one. What geometry do the atoms display?
TWO ELECTRON DENSITIES
Just as two balloons tied together line up, two electron densities adopt a linear arrangement in order to be as far apart from each other as possible and thus minimize their repulsion.
CARBON
The shapes of the s and p atomic orbitals do not allow us to explain the geometry of a LINEAR carbon either. That is why we need to transform (HYBRIDIZE) those orbitals into two new orbitals with a LINEAR geometry. The new HYBRID ORBITALS are called sp because they arise from one s and one p orbital of carbon. Two p orbitals are left over on each carbon, which explain the 'triple bond'.
Practise with molecules containing carbons bonded to two atoms. What geometry do the atoms display?
NITROGEN
The shapes of the s and p atomic orbitals do not allow us to explain the geometry of a triple-bonded nitrogen either. That is why we need to transform (HYBRIDIZE) those orbitals into two new orbitals with a LINEAR geometry. The new HYBRID ORBITALS are called sp because they arise from one s and one p orbital of nitrogen. One of the sp orbitals of nitrogen does not form a bond and holds a lone electron pair. Two p orbitals are left over on the carbon and two on the nitrogen, which explain the 'triple bond'.
Practise with molecules containing carbons bonded to several atoms and nitrogens bonded to one. What geometry do the atoms display?
OXYGEN
Oxygen cannot be bonded to another atom by a triple bond.
Give it a try!