Orgo McMurry Ch. 11 Actual Questions And Answers Verified.
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Course
MCMURRY
Institution
MCMURRY
Alkyl halides do one of two things when they react with a nucleophile/base, such as a hydroxide ion... - correct answer (1) undergo SUBSTITUTION of the X group by the nucleophile
OR
(2) undergo ELIMINATION of HX to yield an alkene
carbon-halogen bonds in al...
Alkyl halides do one of two things when they react with a nucleophile/base, such as a hydroxide ion... -
correct answer (1) undergo SUBSTITUTION of the X group by the nucleophile
OR
(2) undergo ELIMINATION of HX to yield an alkene
carbon-halogen bonds in alkyl halides are polar and the carbon atoms are electron-poor, thus, alkyl
halides are ELECTROPHILES
Nucleophilic Substitution Reactions - correct answer -each step involves the
substitution of one nucleophile (Cl- or OH-) by another
-one of the most common and versatile reaction types in organic chemistry
Alkyl P-Toluenesulfonate - correct answer = a tosylate (Tos)
Note:
-for practical purposes, the ENTIRE tosylate group acts as if it were simply a halogen substituent
-when you see a tosylate substituent in a molecule, tell yourself that you're dealing with an alkyl halide!
Second-Order Reaction - correct answer = a reaction in which the rate is linearly
dependent on the concentrations of two species
Rate Equation (of second-order rxn) - correct answer = expression of the second-
order dependence of the nucleophilic substituion reaction
-you can see, as either [RX] or [-OH] changes, the rate of the reaction changes PROPORTIONATELY
SN2 Reaction - correct answer short for: substitution, nucleophilic, bimolecular
, -the essential feature of the SN2 mechanism is that it takes place in a SINGLE step without intermediates
when the incoming nucleophile reacts with the alkyl halide or tosylate (the SUBSTRATE) from a direction
180 degrees opposite the group that is displaced (the LEAVING GROUP); resulting in an umbrella-like
inversion of configuration at the carbon atom
-as the nucleophile comes in on one side of the substrate and bonds to the carbon, the halide or tosylate
departs from the other side, thereby INVERTING the stereochemical configuration
-the reaction is kinetically SECOND-ORDER and is strongly inhibitied by increasing steric bulk of the
reactants
-SN2 reactions are favored for PRIMARY and SECONDARY substrates
Bimolecular - correct answer ...means two molecules, nucleophile and alkyl halide,
take part in the step whose kinetics are measured (rate-determining step=RDS)
Illustrated SN2 Mechanism - correct answer Reaction of (S)-2-bromobutane with
HO- to give (R)-2-butanol:
-the SN2 reaction occurs when an electron pair on the nucleophile Nu- forces out the group X:-, which
takes with it the electron pair from the former C-X bond (happens thru a ts)
Transition State of SN2 - correct answer -the new Nu-C bond is partially forming at
the SAME time that the old C-X bond is partially breaking and in which the negative charge is SHARED by
both the incoming nucleophile and the outgoing halide ion
-the ts for this inversion has the remaining three bonds to carbon in a PLANAR arrangement
Effects of Changes in Reactant and ts Energy Levels on Rate - correct answer (a) a
higher reactant energy level (red) corresponds to a FASTER reaction (smaller Ea)
(b) a higher transition-state level (red) corresponds to a SLOWER reaction (larger Ea)
Note: some SN2 rxn are fast and some are slow; can take place in high or low yield
SN2 Reactivity - correct answer
Energy Diagrams: Effects on SN2 Rxn - correct answer Graphs display effects of:
(a) Substrate
(b) Nucleophile
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