1. Consider the Diels-Alder cycloaddition reaction below and complete parts (a)-(b) below.
(a) Draw the major regioisomer (or in other words, constitutional isomer) expected to form. Also,
draw appropriate resonance structures to explain why only one constitutional isomer is expected
to form. Discuss the interactions between the diene and dienophile that govern this constitutional
isomer being the only one expected.
The dienophile is the target and the diene is the
attacker in this chemical process It occurs
spontaneously when the temperature rises and no
dddational catalyst is required
The location of the new formed double bond
critisal to the Diels Alder process The diene’s
additional electrons in this reaction enable it to
bind with the dineophile consider it as a giver
where the diene is and the dienophile as a taker
This unique configuration where the diene has a
carbonyl group closeby results in the production
of asingle kind of product
(b) Redraw the regioisomer from part (a) and show the appropriate stereochemistry using correct
dash/wedge notation expected for the major product. Discuss if this is the endo or exo
diastereomer and draw a transition-state intermediate to help illustrate why this diastereomer is
favored. Also, discuss if you believe this diastereomer is chiral or achiral. If it is chiral, also
discuss if you think it will be formed as an equal mixture of two enantiomers (known as racemic).
2. Consider the reaction below and complete parts (a)-(c): (Complete a to c in the next pages)
(a) When the molecule below is treated with HBr at high temperatures, the 1,2-addition
product predominates, rather than the 1,4-adduct. Draw this product and explain this result.
Use appropriate resonance structures to illustrate.
on 0 x
TWO distinct products withdistinctshapes are produced intheDieldsAlder
process calling one of thesegoodsthe endo product it is morewidely
availablethantheother whilethe lesscommon isreferred to as the
exo product Thearrangement oftheatoms is what causes us to obtain
more oftheendoproductthe carbonylgroupsin the dienophilewhichareelectrontakers arecloserto the hydrogens in the dienewhichare similarto electron givers theendo product is preferred in this arrangment
while bothproducts presentarechiralcompounds
(b) Indicate if this product is (i) achiral, (ii) chiral and racemic, or (iii) chiral, non-racemic.
Discuss how you know this to be true.
12 Addition stable
Hot n c s
e 112addition is more stable
we note that the product contains a unique C
atom that has theability to form many mirror
image forms of the compound Because of this the resultis chiral
meaning it has a separate forms from the leftand right hands Moreover during thereaction a laubocation
occurs in this molecule when a carbocation ofcurl the
resorting protest usually consists of a mixture ofequal parts left and right handedforms The carbocationis a flat planar structure and the nucleophile an approachit from any side which iswhy this is rettered to as aracemic mixture
in contusion the result is a racemic mixture that is chiral
consisting of two distin t mirror image form that
coexist in equal amounts
(c) Is this product the thermodynamic product or kinetic product? Discuss what led you to this
3. Using the carbon sources provided and any other necessary reagents needed, propose a viable
synthesis for the product shown. Your synthesis must include a Diels-Alder reaction. For each
step in your synthesis be sure to show the reagents/conditions necessary for that step and also draw
the major product expected for each step leading to the product. You will also need to use reactions
discussed in previous chapters as well.
T temperature reactions have a tendency to favor
the creation of compounds known as thermodynamic
Products This is supported by the fact that th
reactants have more energy at P temperatures
enablingthem to go pastenergy barriers and arriveat a more stable end state The thermodynamicproduct is this stable state whim is preferred inthese circumstances due to it byenergyAs a result a product that forms at p temp is
probably thermodynamic meaning it the reactionsmore stable and desired result
want a t p a
1 3 o no