To calculate the distance you have said at 1:16 that whether we calculate from left hand peak or right hand peak we should get the same answer but we dont. Even in my work that I have to submit I am not getting same. Is this normal in HNMR?
great video! two questions: 1: how do you get 7.2 Hz from plugging in 500 MHz at 3:41 .. wouldn't it be 7.1 * 10^6? Hz ? 2: I thought the coupling constant was supposed to be independent from the external magnetic field? why do we multiply it by 500 then?
Hi, the ppm cancel out the MHz, as you have 10^-6 x 10^6. So we just omit both from the calculation for shorthand. The coupling constant in Hz IS independent of the applied field, but because we are starting our calculation with ppm, which are dependent on field, then we need to take the field into account. 1 ppm on a 500 MHz spectrometer is a different number of Hz (500) from what it would be on a 400 MHz instrument (400 Hz) so we need to take this into account in the conversion from ppm to Hz.
Hi, carbon-13 NMR spectra are almost always run without coupling (it is removed in the experiment) as it tends to make the signals overlap (and therefore it gets really difficult to see what's going on). We would normally use 2-dimensional NMR methods to determine carbon coupling constants.
