¹H and ¹³C NMR: from spectrum to structure

$$\delta = \frac{\nu - \nu_{\text{TMS}}}{\nu_0} \times 10^6$$ in ppm, with $\nu_0$ the spectrometer frequency; TMS sets $\delta = 0$. $\delta$ does not depend on the instrument. An electronegative neighbour (O, halogen, C=O) thins the electron cloud that shields the nucleus: the proton is deshielded, $\delta$ goes up.