CHEM 245- Unit 2
Quiz yourself by thinking what should be in
each of the black spaces below before clicking
on it to display the answer.
Help!
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| all reactions of benzene are | substitution reactions (to keep aromatic ring structure)
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| electron donating groups bond at | 50% ortho, 50% meta
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| electron withdrawing groups bond at | 81% meta
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| rules for determining aromaticity | cyclic, p-orbital, every p-orbital must overlap, pi cloud must contain an odd pair of electrons (4n+2 total electrons)
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| 2 most important aromaticity rules | cyclic, 4n+2 total electrons
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| when do molecules become non-superimposable mirror images? | >2 substitutions
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| clockwise stereochemistry | R
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| counterclockwise stereochemistry | S
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| chiral | not identical to its mirror images
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| achiral | has an internal plane of symmetry
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| clockwise (optically) | dextrorotatory (+)
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| counterclockwise (optically) | levorotatory (-)
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| diastereomer | non-superimposable, non-mirror images
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| do diastereomers have the same physical properties? | no
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| do enantiomers have the same physical properties? | yes
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| # of stereoisomers | 2^(chirality centers)
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| meso compounds | mirror image, rotate 180 is the same as original
*have chirality centers, but achiral because of the mirror plane
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| organohalide elimination trend | more stable with tertiary compounds
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| rate law SN2 reactions | k[Nu][R3C-X]
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| SN2 reactions | occur in a single step without an intermediate
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| SN2 rates | fastest with fewest substitutions; less electronegative anions=better
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| SN2 leaving groups | gases are best; stable anions of strong acids 2nd
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| what does SN2 stand for? | substitution nucleophilic bimolecular
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| what does SN1 stand for? | substitution nucleophilic unimolecular
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| rate law SN1 reactions | k[starting material]
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| SN1 only occurs under ____ conditions | neutral or acidic
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| RDS SN1 | carbocation formation
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| are SN1 stereoselective? | nope
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| SN1 leaving groups | similar to SN2; less electronegative anions; H2O neutral, OH acidic
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| rate law E2 | k[reactant][base]
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| E2 requires | an antiperiplanar relationship between a H and LG
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| acyclic E2 | more highly substituted alkene is formed (same as cyclic if available)
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| E1 rate law | k[starting material]
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| if substrates that work well with both E1 and SN1 are combined... | a mixture of SN1 and E1 products will form
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| primary alkyl halides will use what mechanism(s)? | SN2 if good nucleophile present
E2 if no good nucleophile (base like (CH3)3O)
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| secondary alkyl halides will use what mechanism(s)? | SN2 if good nucleophile present- weakly basic
E2 if no good nucleophile (base like (CH3)3O)
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| tertiary alkyl halides will use what mechanism(s)? | SN1 or E1 under acidic or neutral
E2 if basic
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| SN2 needs an available ___ to occur | sigma *
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| SN1 won't occur if _____ is happening on the molecule | ring strain
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| E2 likes what base? | t-butoxide
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| E1 makes a | double bond
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