CHEM1112 Lecture Notes - Lecture 1: Orbital Hybridisation, Catenation, Electronegativity
16 May 2018
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• Determine geometry and hybridization state for each carbon, nitrogen and oxygen atom in a
molecule
Carbon: 1s2, 2s2, 2p2. Valence 4 electrons, mid-range electronegativity. C-C, C-H bonds are strong and
stable. Can bond to itself, other metals, heteroatoms. Geometrically flexible, capable of catenation
(forms covalent bonds with other Carbons), forms chains, rings. Shares 4 electrons, form 4 covalent
bonds- 2 2s and 2 2p orbitals hybridize (2s+ 2p) --> 4 sp3 orbitals.
Hybridization: if a 2s mixes with three 2p orbitals --> 4sp3
Sp2: 2s orbital mixes with 2 2p orbitals --> 3 sp2 hybridized orbitals. Eg: 3 identical bonds + one different
one= 3x single bonds + 1 different one
Alkynes: 2s orbital mixes with 1 2p orbital --> 2 sp orbitals (because there is only one 2p orbital being
hybridized with the 2s)
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Multiple bonds and heteroatoms= functional groups. Molecules held together by Van de Waals forces:
increase with increasing size, MP and BP increase with size.
Alkenes: inert, good substrates for radical reactions, a lot of energy formed in combustion, common in
fuel, short chained= burn efficiently.
• Interconvert structural and stick formula and stick representations of a molecule
Simple, shows structural information, heteroatoms shown. Geometry depends on hybridization,
indicating bond angles of 120* or 180*.
• Convert a stick structure into a molecular formula
Condensed-- structural-- stick
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• Recognise and name functional groups in a molecule
• Name simple alkanes and give IUPAC names
• CnH2n+2
• 109.5* bond angle, 110pm bond length
• Sigma bonds from overlap of C sp3 orbitals with H 1s orbitals
• Distinguish between conformational and configurational isomers of alkenes
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Document Summary
Determine geometry and hybridization state for each carbon, nitrogen and oxygen atom in a molecule. Geometrically flexible, capable of catenation (forms covalent bonds with other carbons), forms chains, rings. Shares 4 electrons, form 4 covalent bonds- 2 2s and 2 2p orbitals hybridize (2s+ 2p) --> 4 sp3 orbitals. Hybridization: if a 2s mixes with three 2p orbitals --> 4sp3. Sp2: 2s orbital mixes with 2 2p orbitals --> 3 sp2 hybridized orbitals. Eg: 3 identical bonds + one different one= 3x single bonds + 1 different one. Alkynes: 2s orbital mixes with 1 2p orbital --> 2 sp orbitals (because there is only one 2p orbital being hybridized with the 2s) Molecules held together by van de waals forces: increase with increasing size, mp and bp increase with size. Alkenes: inert, good substrates for radical reactions, a lot of energy formed in combustion, common in fuel, short chained= burn efficiently.
