Delocalization of electrons Conjugated double bond: switching between single-bond and double bond TT-bond electrons in the conjugated system are delocalized Conjugated chain EXample Same chain alternative version C6H(benzene) Delocalized n-bonds CH=CH-CHECH Benzol ring
Delocalization of Electrons Conjugated double bond: switching between single-bond and double bond. π-bond electrons in the conjugated system are delocalized. Example: C6H6 (benzene) CH2=CH-CH=CH2 11
Conjugated TT Bond Conjugated T bond molecules/ions All conjugated atoms are in a same plane, each giving a p-orbital to form the conjugated Tr bond Total T electron numbers 2* p-orbitals nnm(formed by n p-orbitals and m p-electrons) m=n: Most of the organic conjugated molecules m>n: double bond next to an atom with lone pair e (e.g. N,O, Cl, S) m<n: cations, e.g(CH2=CH-CH3)*, (C6H5)3C+
Conjugated π Bond Conjugated π bond molecules/ions: All conjugated atoms are in a same plane, each giving a p-orbital to form the conjugated π bond; Total π electron numbers < 2 * p-orbitals Πn m (formed by n p-orbitals and m p-electrons) m=n: Most of the organic conjugated molecules; m>n: double bond next to an atom with lone pair e (e.g. N, O, Cl, S) m<n: cations, e.g. (CH2=CH-CH3)+, (C6H5)3C+ 12
Molecular Orbital Method Textbook, page 386, 10.90: For the compound H2C=CHCOOCH3 (a) draw a complete structure; (b) How many pi-bonds and how many sigma bonds are in this molecule? (c)What hybridizations are applied for each carbon? (d)How many electrons are de-localized? (e) how many atoms lie in the same plane? (t What are the bond angles between each bond?
Molecular Orbital Method Textbook, page 386, 10.90: For the compound H2C=CHCOOCH3, (a) draw a complete structure; (b) How many pi-bonds and how many sigma bonds are in this molecule? (c) What hybridizations are applied for each carbon? (d) How many electrons are de-localized? (e) How many atoms lie in the same plane? (f) What are the bond angles between each bond? 13
HOMO and lumo HOMO: Highest occupied Molecular Orbital LUMO: Lowest Unoccupied Molecular orbital LUMO UMO LUMO LUMO LUMO h HOMO OMO HOMO HOMO CI AICI3 Acceptor Hc-C—o HOMO LOMO are very useful in predicting chemical reactivity, opticallelectrical properties
HOMO and LUMO HOMO: Highest Occupied Molecular Orbital LUMO: Lowest Unoccupied Molecular Orbital HOMO & LOMO are very useful in predicting chemical reactivity, optical/electrical properties. 14