diels alder Flashcards
what’s the pattern of a diels alder
break 3 pi bonds, form 2 single bonds and a pi bond
How many pi electrons are involved in diels alder
6
what is the conformation requirement for a diels-alder reaction
the pi bonds must be in the s-cis conformation
which conformation of a diene is more stable? s-cis or s-trans? which way does the equilibrium lie
s-trans is more stable due to the steric effects seen in s-cis, equilibrium favors s-trans as it is lower energy
how many pi electrons are in the diene
4
how many pi electrons are in the dienophile
2
how do the 6 pi electrons in a diels alder react
in a concerted mechanism
how many carbon carbon bonds are made in a diels alder reaction
2
what does the diels alder reaction ALWAYS make?
six membered ring
what type of reaction is a diels alder?
substitution
addition
rearrangement
addition
what is the product of a diels alder called
a adduct
what in the transition state for a diels alder reaction makes it occur readily at room temperature
the moving of 6 pi electrons creates a transition state that closely resembles the resonance hybrid, this makes the energy very low and the product forms readily at room temperature
what is the normal demand for a diels alder reaction defined by
the diene has an electron donating group and the dienophile has a electron withdrawing group
what is the effect of having an EDG on a diene
it brings the energy up
what is the effect of having an EWG on the dienophile
it brings the energy down
what is the inverse diels alder reaction defined by
the diene has an electron-withdrawing group and the dienophile has an electron-donating group
What is an electron donating group
electron donating groups are electron rich like an ether or alchohol
why is cyclopentadiene highly reactive
it forces the diene to be cis
what are electron withdrawing groups
anything that pulls electrons towards itself
halogens or carbonyls
where is the bridgehead carbon in bicyclic adduct from a diels alder
it is above the plane
what is the endo product
it is the kinetic product, it has a more stable transition state and is formed in cooler temperatures
it is higher energy due to the concave nature
the substituents are pointed down
what is the exo product
it is when the groups are pointed externally and up (wedge), the product is more stable since there are less steric interactions
this product is thermodynamically favored
what product forms at 0°C for diels alder?
the kinetic endo product with the groups pointing down
what product forms at 40°C for the diels alder
the thermodynamic exo product with the groups pointing externally out
what is the stereoisometric relationship between the endo and exo product
they are diastereomers
what type of reaction is the diels alder in relation to stereochemistry
it retains stereochemistry
what is the difference between stereoselective and stereospecific
stereoselective is the favoring of a certain stereoisomer
stereospecific is a chemical reaction where the stereochemistry of the reactants directly determines the stereochemistry of the products
