1 Due to the high degree of regio-and stereoselectivity (due to the concerted mechanism), the Diels-Alder reaction is a very powerful reaction and is widely used in synthetic organic chemistry.2  The reaction usually thermodynamically favourable due to the conversion of 2 &#960 -bonds into 2 new stronger &#963-bonds. Due to the high degree of regio-and stereoselectivity (due to the concerted mechanism), the Diels-Alder reaction is a very powerful reaction and is widely used in synthetic organic chemistry.
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.
After you visit your doctor, share your symptoms and undergo a routine physical in which the physician listens to your heart and lungs, he or she may determine that you might have a heart valve disorder. An echocardiogram is typically ordered both to verify the diagnosis and to reveal the extent of the problem. As the echocardiogram uses sound waves, the technician and physician can view your heart beating. Typically a standard, two-dimensional echocardiogram takes about 30 minutes to complete.