Tilt 45

Tilt 45 and Homonuclear J-resolved 2D-NMR spectroscopy (Not available in Mnova Lite):

Homonuclear J-resolved two-dimensional NMR spectroscopy is used to generate one frequency dimension representing chemical shifts and another with coupling constant information. This technique is most frequently used with homonuclear J-resolved spectra where the effect of couplings in the f2 dimension is not required.

The sequence:

(where d1 is for relaxation and t1/2 and t2 are the two time dimensions for the two-dimensional experiment) uses the 180º pulse to refocus chemical shifts during t1.

In a J-resolved spectrum, the 1H frequencies are found on the horizontal axis (f2) with the normal 1D spectrum displayed at the top while the vertical axis (f1) contains only proton-proton coupled multiplets, each centered about a zero frequency point. Then, the 2D J-resolved spectrum may be 'tilted 45º' (a projection at an angle of 45º) along a horizontal line through the center of the matrix, so that all the lines of each multiplet line up in the f1 dimension. Each row of the 2D matrix is shifted by an amount proportional to its distance from the middle of the spectrum. If all the individual spectra are now added together, the result is a 1H decoupled NMR spectrum which is normally shown above the 2D spectrum.

Finally, the user could clean up the spectrum by symmetrizing it about the f1 = 0 Hz row. As it is explained in the previous chapter, this consists of comparing the intensities in the spectra equally spaced above and below the f1 = 0 Hz row and taking the smallest value.

This command is available by following the menu 'Processing/More Processing/Tilt 45'.