Carbon-13 NMR satellite

Carbon satellites always appear as an evenly spaced pair around the main 1H peak.

Carbon satellites (and spinning sidebands) should not be confused with impurity peaks.

Carbon satellites can be used to obtain structural information, which is not available by looking at the main peaks in the NMR spectrum.

For example, it is not possible to tell whether stilbene (Ph-CH=CH-Ph) has a cis- or trans- double bond just by examining at the main peaks in the 1H NMR spectrum.

However, 1% of the stilbene molecules will have a 13C atom on one of these double bond carbons (i.e. Ph-13CH=12CH-Ph).