In a normal demand DielsâAlder reaction, the dienophile has an electron-withdrawing group in conjugation with the alkene; in an inverse-demand scenario, the dienophile is conjugated with an electron-donating group.Dienophiles can be chosen to contain a masked functionality.n a normal demand DielsâAlder reaction, the dienophile has an electron-withdrawing group in conjugation with the alkene; in an inverse-demand scenario, the dienophile is conjugated with an electron-donating group.
A standard echocardiogram or a fetal echocardiogram test usually takes about 30 to 60 minutes. A stress echocardiogram usually takes between 60 and 90 minutes.
Key points. 1  An echocardiogram is a test that takes pictures of the heart. 2  The test does not hurt. It takes between half an hour and an hour and a half to do. 3  A child needs to be still during the test, so some children need to be sedated or put to sleep for the test.