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.
Fetal echocardiography is a test similar to an ultrasound. This exam allows your doctor to better see the structure and function of your unborn childâs heart. Itâs typically done in the second trimester, between weeks 18 to 24. The exam uses sound waves that âechoâ off of the structures of the fetusâ heart. A machine analyzes these sound waves and creates a picture, or echocardiogram, of their heartâs interior.