CHEM 281 Lecture Notes - Lecture 4: Molecular Orbital Diagram, Substituent, Aromaticity

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16 Sep 2015

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For only the aromatic molecules below, so how many -electrons are present in each aromatic system. Using frost-musulin diagrams, and only 4 aromatic molecules above, generate the relative frontier molecular orbital diagram for your choices. Nr2ohsroronhororrarxoronr2oorcnso3hcx3no2nr3substituentrate e ectregiochemistrystrongly activatingortho, paramoderately activatingortho, paraweakly activatingortho, paraweakly deactivatingortho, paramoderately deactivatingmetastrongly deactivatingmetashow the mechanism for each of the electrophilic aromatic substitutions below. Deduce the identify of the structure with the molecular formula c8h7no that exhibits the following ir, 1h nmr and 13c nmr spectra. Deduce the identify of the structure with the molecular formula c9h9no3 that exhibits the following ir, 1h nmr and 13c nmr spectra. Deduce the identify of the structure with the molecular formula c9h11br that exhibits the following ir, 1h nmr and 13c nmr spectra. Deduce the identify of the structure with the molecular formula c11h17no that exhibits the following ir, 1h nmr and 13c nmr spectra.

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1. Of Huckel's requirements for aromaticity, only this one is NOT required in the case of some compounds to be considered aromatic? 8. Which sequence of reagents would produce b) The system must be monocyclic. c) There must be (4n + 2) Ï electrons. d) The Huckel number of electrons must be completely 2. Zn(Hg), conc. HC delocalized. 2. 4-amino-2-chlorobenzaldehyde is NOz H2N NO2 3. Which of the following compounds are aromatic? Hint: 9. Refer to the following list of possible answers: So ) halogen h) RC-O D diazonium ion a. What group weakly activates benzene to b. What group slightly deactivates benzene to SeAr because a) I and II only c)I, II and â ¢ b) II and III only d) I and IlI only SAr by a +I e-donor inductive effect? of its-I withdrawal inductive effect, but is an ortho-/para- director because of its +R resonance e-donor 4. Which one of the following compounds is anti-aromatie? c. What group inhibits Friedel-Crafts alkylation and acylation d. What species is the electrophile e. What species is formed when but strongly activates a halo benzene to S&Ar because of its strong -R e-withdrawal resonance effect? In which case is the indicated unshared pair of electrons Nora contributor to the Ï aromatic system? 5. in Friedel-Crafts acylation? aniline reacts with NaNO HCVS? 10. Arrange these benzene compounds in order of decreasing (fastest to slowest) SeAr reactivity: . Cyclopentadiene is unusually acidic for a hydrocarbon a) The carbon atoms are all sp hybridized. b) Cyclopentadiene is aromatic. c) Removal of a proton from cyclopentadiene yields an a) III > IV > 11 > 1 c) IV I> III d) IV > â ¡ > I> aromatic anion. d) Removal of a hydride ion from cyclopentadiene What might be predicted to happen when the following substance undergoes Friedel-Crafts acylation? produces an aromatic cation. 11. Recalling that benzene has a resonance energy of 152 k mol and naphthalene has a resonance energy of 255 k mol', predict the two positions which would be occupied by bromine when phenanthrene (below) undergoes addition of Brã (circle two numbers). a) Substitution occurs in ring A, o- to the methylene gro b) Substitution occurs in ring A, o-to the nitro group. c) Substitution occurs in ring A, m- to the methylene g d) Substitution occurs in ring B, o-/p- to the methylene e) Substitution occurs in ring B, m. to the methylene 10 9

Part 2 â Using the 4 C-C ?-bonding acetylene orbitals provided above (place these below a2 of ML4 in relative energy), their related C-C ?*-antibonding orbitals (place these at a higher energy than 2a1 of ML4), and the ML4 fragment orbitals that are already provided, generate an abridged molecular orbital diagram for 1. You do not need to provide molecular orbital sketches, but drawing them will help you visualize your answer.

CHEM 281 Lecture Notes - Lecture 4: Molecular Orbital Diagram, Substituent, Aromaticity

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