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.
An echocardiogram (echo) is a test that uses high frequency sound waves (ultrasound) to make pictures of your heart.he test is also called echocardiography or diagnostic cardiac ultrasound. Quick facts. 1  An echo uses sound waves to create pictures of your heartâs chambers, valves, walls and the blood vessels (aorta, arteries, veins) attached to your heart. 2  A probe called a transducer is passed over your chest.