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. The 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.uick 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.