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.
1 Echocardiogram (EKG or ECG): Also known as a cardiac echo, this test uses sound waves to take pictures of your heart.  Holter monitor: This monitor is worn for at least 24 hours while you go about your normal activities. It allows your doctor to track changes in your heartâs rhythm throughout the day.