The Carbonyl Group

• C has sp3 hybridisation for alkanes forming a tetrahedral shape
• C has sp2 hybridisation for alkanes for the sigma and pi bond
• The carbonyl C is sp2 hybridised and trigonal planar with bond angles of 120*, there is one sigma bond and one pi bond
• The electronegative O in the carbonyl group means the C=O bond is polarised, making the carbonyl C electron deficient. There is an uneven sharing of electrons in C=O bond
• Aldehydes and ketones are polar molecules because the C=O bond has a dipole moment - their polarity makes aldehydes and ketones have higher BP than alkenes of similar Mr, but a lower BP than alcohols of same Mr (aldehydes and ketones are not hydrogen bond donors, are hydrogen bond accepts so are soluble in water)
• Carbonyl C is electrophilic as O is electronegative so group is polarised. The pi bond is weak and easily broken, the sigma bond is stronger
• Main mode of reaction for carbonyl compounds is to react with nucleophiles - carbonyl group is statically vey accessible
• Carbonyl group has trigonal planar structure so carbonyl C is uncrowded
• Carbonyl group can attack through nucleophilic attack at C