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29 Cards in this Set
- Front
- Back
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clockwise polarimeter rotation
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dextrorotary (+)
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counterclockwise polarimeter rotation
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levorotary (-)
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Optical Purity (enantiometric excess)
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%ee=100[a]mixture/[a]pure enantiomer
%ee=%major-%minor |
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%major enantiomer
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=%ee + [(100-%ee)/2]
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%minor enantiomer
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=(100-%ee)/2
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max # stereoisomers possible
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2^n (n=#chiral carbons)
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meso compound
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compound with chiral carbons that is achiral as a whole due to symmetry and even #chiral carbons
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rxns producing chiral carbons
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chirals produced from carbocation or radical (free rad. halogenation, hydration of alkenes)
electrophyilic additions to alkenes w/out carbocations or radicals using achiral substrates (hydrogenation, halogenation, hydroboration-oxidation) |
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chiral pool
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used to separate enantiomer mixtures--mix w/ separate pure enantiomer reagent, separate w/ techniques
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transhalogenation
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substituting one halogen atom with a different halogen atom
useful with preparation of alkyl fluorides and alkyl iodides |
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Favor Sn1
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3' RX
weak C-X bonds (RI) weak nucleophiles (neutral species-water, alcohol, carboxylic acids) polar protic solvents |
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Favor Sn2
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CH3X and 1' RX
strong C-X bonds (RCl) strong nucleophiles (anions, neutral amines) non-polar solvent polar-aprotic solvent |
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Favor substitution
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low steric hindrance
small nucleophiles/bases low rxn temps weaker bases |
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Favor elimination
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high steric hindrance
large nucleophiles/bases high rxn temps stronger bases |
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elimination vs. substitution w/ alkyl halides
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1' strong y- = Sn2 major/E2 minor
2' strong y- = Sn2/E2 competeing 2' weak y- = Sn1/E1 competeing 3' strong y- = E2 only 3' weak y- = Sn1/E1 competing |
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making elimination major product regardless
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use large base (tert-butoxide) at high temps
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sulfonates
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ROSO2R
treated like halides but are a better leaving group ROMs and ROTs favors Sn2 |
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requirements to abstract a proton to form an alkyne
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pKa of BH must be higher than pKa of HA
(HA must be stronger acid than BH) |
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bases for deprotonating alkynes
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MNH2 (NaNH2, KNH2)
RLi alkanes ammonia |
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Alkylation of Terminal Alkynes
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2 steps
acid-base chem to abstract proton Sn2 nuc substitution restricted to primaries |
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Prep of alkynes
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dehydrohalogenation
equivalents of NaNH2 needed (extra needed for terminals) |
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Reactions of Alkynes
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Hydrogenation
Metal ammonia reduction hydrohalogenation hydration halogenation hydroboration-oxidation ozonolysis |
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Hydrogenation
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H2 (w/ metal, Ni)
produces alkane produces alkene w/ Lindlar Pd syn addition = cis |
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Metal Ammonia Reduction
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trans-alkenes
reagents - M(Li,Na,K) NH3(l) combines radical & ionic steps |
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Hydrohalogenation
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markovnikov
produces alkenes w/ 1eq X produces alkanes w/ 2eq X gem dihalides from more stable carbocation anti-markovnikov if used w/ radical initiator (ROOR, HBr, light) |
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Hydration
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Markovnikov
H2SO4 and H2O acid catalyzed product always a ketone (internals produce mixture of 2 ketones) |
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Hydroboration-Oxidation
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anti-markovnikov
base catalyzed 1.BH3 2. H2O2/NaOH product always aldehyde for terminals always ketone for internals |
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Halogenation
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1eq X2
anti addition = trans 2eq X2 tetrahalide products |
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Ozonolysis
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products always carboxylic acids
1.O3 2. H2O |
