Final Exam Flashcards
sulfonates
- So3 groups
- S is double bonded to two oxygens and single bonded to the third oxygen
- very good leaving groups because of resonance
- made from corresponding alcohol in a reaction
alcohols in elimination and substitution reactions
they are bad leaving groups so they get converted into good leaving groups by sulfonates or strong acids
-OH as a reagent
strong nucleophile and a strong base
pyridine
non-nucleophilic base
how is the alpha carbon respresented in sulfonate reactions?
with R
stereochemistry of OH and sulfonate reactions
stereochemistry does not change because the sulfur gets attacked
how are alcohols used as starting materials in reactions?
to make alkyl halides and alkenes
What needs to occur if an alcohol is the reactant?
strongly acidic conditions are needed to protonate OH into H2O because H2O is a good leaving group
HBr as a reagent
strong acid, not a nucleophile or base
Br as a reagent
strong nucleophile only, encourages substitution
HX mechanism for alcohols
- results in a substitution reaction
- primary alcohols react Sn2
- secondary and tertiary alcohols react Sn1
what conditions are protic conditions?
strongly acidic
elimination of alcohols
-favored by H2SO4 because the byproduct of the first step
-favored by heat
-
what do protic conditions favor?
E1 for secondary and tertiary substrates
retrosynthesis
thinking and synthesizing backwards
addition reactions
- opposite of elimination reactions
- pi bonds act as lewis bases, nucleophiles or bronsted lowry bases
- at temperature dependent equilibrium with elimination reactions
- typically add 2 atoms across a pi bond
- usually exothermic
what does 🔼G represent in elimination reactions?
competition between the enthalpy and entropy term
low temperature 🔼G reactions
- entropy is small
- enthalpy dominates
- 🔼G
- K>1
- products favored
high temperature 🔼G reactions
- entropy is large
- entropy dominates
- +🔼G
- K<1
- reactants favored
why are addition reactions usually exothermic?
a pi bond is broken and 2 sigma bonds are formed
enthalpy for exothermic addition reactions
neagtive
entropy of addition reactions
entropically unfavorable(- 🔼S) because 2 molecules become one
how can an addition reaction be favorable if the entropy is unfavorable?
enthalpy magnitude outweighs unfavorable affect of enthalpy
which types of addition reactions are most closely related?
halogenation and halohydrin formation