Carbon satellites in

physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which r ...

and

spectroscopy Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter wa ...

, are small peaks that can be seen shouldering the main peaks in the

nuclear magnetic resonance Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong constant magnetic field are perturbed by a weak oscillating magnetic field (in the near field) and respond by producing an electromagnetic signal with a ...

(NMR)

spectrum A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colors i ...

. These peaks can occur in the NMR spectrum of any NMR active atom (e.g. ¹⁹F or ³¹P NMR) where those atoms adjoin a carbon atom (and where the spectrum is not ¹³C-decoupled, which is usually the case). However, Carbon satellites are most often encountered in

proton NMR Proton nuclear magnetic resonance (proton NMR, hydrogen-1 NMR, or 1H NMR) is the application of nuclear magnetic resonance in NMR spectroscopy with respect to hydrogen-1 nuclei within the molecules of a substance, in order to determine the struc ...

. In the example of

, these peaks are not the result of proton-proton coupling, but result from the coupling of ¹H atoms to an adjoining ¹³C atom. These small peaks are known as carbon satellites as they are small and appear around the main ¹H peak i.e.

satellite A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotope ...

(around) to them. Carbon satellites are small because ¹³C only makes up about 1% of the atomic carbon content of

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...

, the rest of the carbon atoms are predominantly NMR inactive ¹²C. Carbon satellites always appear as an evenly spaced pair around the main ¹H peak. This is because they are the result of 1% of the ¹H atoms coupling to an adjoined ¹³C atom to give a wide doublet (¹³C has a spin of a half). Note, if the main ¹H-peak has proton-proton coupling, then each satellite will be a miniature version of the main peak and will also show this ¹H-coupling, e.g. if the main ¹H-peak is a doublet, then the carbon satellites will appear as miniature doublets, i.e. one doublet on either side of the main ¹H-peak. For other NMR atoms (e.g. ¹⁹F or ³¹P atoms), the same applies as above, but obviously where the proton atom is replaced with that other NMR active atom e.g. ³¹P. Sometime other peaks can be seen around ¹H peaks, these are known as spinning sidebands and are related to the rate of spin of an

NMR tube An NMR tube is a thin glass walled tube used to contain samples in nuclear magnetic resonance spectroscopy. Typically NMR tubes come in 5 mm diameters but 10 mm and 3 mm samples are known. It is important that the tubes are uniforml ...

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

Uses

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

NMR Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong constant magnetic field are perturbed by a weak oscillating magnetic field (in the near field) and respond by producing an electromagnetic signal with ...

. This usually occurs when the purely ¹²C compound is symmetrical but where the 1% of the compound which has a ¹³C atom in it is no longer symmetrical. For example, you can not tell if

stilbene Stilbene may refer to one of the two stereoisomers of 1,2-diphenylethene: * (''E'')-Stilbene (''trans'' isomer) * (''Z'')-Stilbene (''cis'' isomer) See also * Stilbenoids, a class of molecules found in plants * 1,1-Diphenylethylene 1,1-Diphenyl ...

(Ph-CH=CH-Ph) has a

cis Cis or cis- may refer to: Places * Cis, Trentino, in Italy * In Poland: ** Cis, Świętokrzyskie Voivodeship, south-central ** Cis, Warmian-Masurian Voivodeship, north Math, science and biology * cis (mathematics) (cis(''θ'')), a trigonome ...

- or

trans Trans- is a Latin prefix meaning "across", "beyond", or "on the other side of". Used alone, trans may refer to: Arts, entertainment, and media * Trans (festival), a former festival in Belfast, Northern Ireland, United Kingdom * ''Trans'' (film ...

double bond In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist betw ...

just by examining at the main peaks in the ¹H NMR spectrum. The =CH- proton does not couple to the adjacent =CH- proton as the molecule is

symmetrical Symmetry (from grc, συμμετρία "agreement in dimensions, due proportion, arrangement") in everyday language refers to a sense of harmonious and beautiful proportion and balance. In mathematics, "symmetry" has a more precise definiti ...

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

couple Couple or couples may refer to : Basic meaning *Couple (app), a mobile app which provides a mobile messaging service for two people *Couple (mechanics), a system of forces with a resultant moment but no resultant force *Couple (relationship), tw ...

to the ¹³C atom to give a wide

doublet Doublet is a word derived from the Latin ''duplus'', "twofold, twice as much",