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.
Standard EEG recording is done in the office and usually lasts an hour. You may be asked to do a sleep-deprived EEG, which requires you to have only 4 hours of sleep. Abnormal brain waves may appear when the body is stressed or fatigued. This exam usually takes 2 to 3 hours.You will be given specific instructions regarding food, drink, and medications that may need to be avoided.). Figure 1. A sample EEG recording showing a focal spike typical of a seizure. There are several different ways to conduct an EEG: 1  Standard EEG recording is done in the office and usually lasts an hour. 2  You may be asked to do a sleep-deprived EEG, which requires you to have only 4 hours of sleep.