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Which of the following compounds is the most reactive dienophile in a Diels-Alder reaction with 1,3-butadiene, #CH_2=CH-CH=CH_2#?

#CH_2=CH-CH=O#
#(CH_3)_2C=CH_2#
#CH_2=CH-OCH_3#
#CH_3-CH=CH-CH_3#
#CH_2=CH_2#

Answer 1

The most reactive dienophile is propenal.

The Diels-Alder reaction

The Diels-Alder reaction is a [2+4]-cycloaddition reaction between a 1,3-diene and an alkene (a dienophile) to form a cyclohexene.

The transition state involves the overlap of the frontier orbitals — usually the HOMO of the diene and the LUMO of the dienophile.

Nature of the Dienophile

Adding an electron-withdrawing group (EWG) to the alkene lowers the energy of the LUMO.

) and cyano (#"C≡N"#) groups.

The groups attached to the dienophile in this question are #"CHO"# (EWG), #"CH"_3# (weakly donating), and #"OCH"_3# (strongly donating).

The most reactive dienophile is the aldehyde — propenal.

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Answer 2

Delilah Anderson

Maleic anhydride is the most reactive dienophile in a Diels-Alder reaction with 1,3-butadiene.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

Which of the following compounds is the most reactive dienophile in a Diels-Alder reaction with 1,3-butadiene, #CH_2=CH-CH=CH_2#?

#CH_2=CH-CH=O# #(CH_3)_2C=CH_2# #CH_2=CH-OCH_3# #CH_3-CH=CH-CH_3# #CH_2=CH_2#

#CH_2=CH-CH=O#
#(CH_3)_2C=CH_2#
#CH_2=CH-OCH_3#
#CH_3-CH=CH-CH_3#
#CH_2=CH_2#