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70 Cards in this Set
- Front
- Back
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Why is cyclobutadiene unstable?
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Its highest lying e- are in nonbonding orbitals
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What are the criteria of an aromatic compound?
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1- structure must be cyclic
2- Each atom must have a nonhybridized p orbital 3-orbitals must overlap - planar 4- delocalized pi electrons must lower the energy |
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what is anti aromatic?
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pi electrons raise e-. Cyclobutadiene is less stable than when it is an open molecule (ring strain)
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What is aliphatic
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cyclic, but doesnt' have overlapping pi orbitals
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Huckels rule?
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aromatic is 4N+2
antiaromatic is (4N) |
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Why does Huckles rule not apply to cyclobutadiene?
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because it isn't planar
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Which of the larger annulenes can attain a planar configuration?
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-14(annulene) 18(annulene)
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Why is cylcopentadine anion aromatic?
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6 pi electrons
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Why is cylcopentadine acidic?
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Very acitic. It can loose a proton and then become a stable aromatic
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What is tropylium?
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a cyclic species with 7 sides
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Which is more stable, a tropylium cation or anion
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cation - it has 6 pi electrons
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How do you create a tropylium cation?
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treat with an aqueous sulfuric acid
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why is tropylium anion difficult to create?
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it is antiaromatic and therefore VERY reactive.
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is this aromatic, non aromatic, or antiaromatic? cyclopropene catiion
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aromatic
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what is pyradine?
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six sided aromatic with a nitrogen
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Is pyradine basic or acidic?
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basic, because the electrons on the nitrogen are easily protonated
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Does the addition of a proton affect the aromaticity of pyradine?
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no
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what is pyrrole?
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cyclic five memebered ring with the formula C4H4NH. Has an NH on the ring. N is sp2 hybridized and the lone pair overlaps. So it is aromatic.
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Why is pyrrole a weak base?
Where is it protonated |
N must be sp3 hyrbidized to abstract a proton, but the e- are busy being aromatic. Pyyrole gets protonated at 2 carbon rather than N
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What is pyramidine?
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6 membered ring, 2 N atoms at the 1, 3
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Who can you tell which is the basic N?
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double bond a the lone pair of hybrid e-
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How can you tell the nonbasic N?
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3 single bonds, long pair in p orbital
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What is imidazole
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5 membered ring,
N#1- double bonded, lone pair not in aromatic N#2single bonded, has an H, lone part of SP2, not basic once both Ns have been protonated they are equal |
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furane
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5-membered ring
O, 2 lone pairs, only one is hybridized |
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Thiophene
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5 membered ring, S, , 2 lone pairs, 3p orbital
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What is Naphthalene?
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C10H8, 2 fused benzene rings, 1o pi electrons
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If resonance goes up, what does reactivity do?
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Reactivity goes down
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The more pi electrons, what happens to resonance?
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electron density increases resonance, so it increases
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Anthracene
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three fused rings in a row
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Phenanthane
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three fused rings like olympics
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Which has a higher reactiivty, anthracene or phenanthrene?
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Phenanthrene because e- density is higher, so resonance is higher, there fore stability is higher. and it is i less reactive
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Which reaction does Anthracene undergo
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1.4 added at 9,10 to five two fully aromatic benzene rings (cis and trans)
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What reaction does Phenathrene undergo?
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1,2 added at he 9, 10. two fully aromatic benzne rigns (cis and trans)
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Why is diamond an electrical insulator
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e- bonds are sigma, can't carry a current
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What holds layers together in graphite?
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vanderwalls
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Whihc is more stable, graphite or diamond?
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graphite, it is more aromatic
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What is fullerene?
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buckyball type
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What does Purine look like?
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2 fused rings,
1) penta has N and NH 2) hexa has 2N |
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What is benzofurane
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benzene with a penta with an :O:
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What is imadole?
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Benzene with a penta NH
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What is benzothiophene
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2 fused rings
1)benzene 2) penta with :O: |
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What is benzimidazole?
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2 fused rings
1)benzene 2) penta with N,NH |
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What is toluene
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Benzene with a CH3
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What is quinoline
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2 fused rings
1)benzene 2) hexa with N: |
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What is aniline
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Benzene with :NH2
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What is phenol?
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Benzene with an OH
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Draw styrene
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Benzene with a vinyl
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What is anisole
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Benzene with an OCH3 attached
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What is acetophenone
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benzene with a carbonyl with a methyl
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what is benzaldehyde
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benzyne, ketone with an H
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what is benzoic acid?
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benzene with a carbonyl with an OH
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what does ortho mean?
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groups at 1,2
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What does Para mean?
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groups at 1,4
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What does meta mean?
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groups at 1,3
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What is a benzyl group?
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Ar-CH2-}
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What is an erene
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an aromatic hydrocarbon
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What is a phenyl group
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6 carbons
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What is the mp in aromatics related to?
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how they pack into crystals, or how symetrical they are. Higher melting points than aliphatic
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Which has a higher mp, o-, m-, p dicholorbenzene?
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para, more symmetrical
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what is boiling point related to?
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dipole moment, the higher the dm, the higher the bp
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Which has a higher bp, o-, m-, p-?
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p- no dipole moment
o- 1,2 (highest dipole moment) m 1,3 |
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are aromatics less dense than water or more dense
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less dense
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how do you identify aromatics in an Ir
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C=C around 1600 (less stiff than normal C=C bonds) and above 3000
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Where are aromtics expressed in HNMR
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7.2
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How do carbonyls, N, or CN groups affect HNMR readings
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they are electronegative, withdraw electrons, so protons are deshielded, and move down field
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How do OH, NH2 groups affect HNMR
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move them upfield
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which protons split in NMR
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non equitable orthos and metas
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Where do aromatics absorb in CNMR
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1220-150
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What is the UV absorbtion of bezene?
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204 and 254 (six small peaks)
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How do groups affect UV
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higher wavelength, move to right.
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