Carbon-13 NMR satellite - AbsoluteAstronomy.com

Carbon satellites are small peaks that can be seen shouldering the main peaks in an NMR

NMR

NMR may refer to:Applications of Nuclear Magnetic Resonance:* Nuclear magnetic resonance* NMR spectroscopy* Solid-state nuclear magnetic resonance* Protein nuclear magnetic resonance spectroscopy* Proton NMR* Carbon-13 NMR...

spectrum. These peaks can occur in the NMR spectrum of any NMR active atom (e.g. ¹⁹F

Fluorine-19 NMR

Fluorine-19 nuclear magnetic resonance is an analytical technique. 19F has a spin of 1/2, and a relative abundance of 100 % and a high magnetogyric ratio, making measurements very fast . Integrals are reliable due to the lack of a nuclear Overhauser effect...

or ³¹P NMR

Phosphorus-31 NMR

Phosphorus-31 NMR spectroscopy is an analytical technique. Solution 31P-NMR is one of the more routine NMR techniques because 31P has an isotopic abundance of 100% and a relatively high magnetogyric ratio. The 31P nucleus also has a spin of ½, making spectra relatively easy to interpret...

) 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 NMR

Proton 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 structure of its molecules. In samples where natural hydrogen is used, practically all of the hydrogen consists of the...

.

In the example of proton NMR

Proton NMR

, these peaks are not the result of proton-proton coupling

Proton NMR

, but result from the coupling of ¹H atoms to an adjoining ¹³C

Carbon-13

Carbon-13 is a natural, stable isotope of carbon and one of the environmental isotopes. It makes up about 1.1% of all natural carbon on Earth.- Detection by mass spectrometry :...

atom. These small peaks are known as carbon satellites as they are small and appear around the main ¹H peak i.e. satellite

Satellite

In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....

(around) to them. Carbon satellites are small because ¹³C

Carbon-13

Carbon-13 is a natural, stable isotope of carbon and one of the environmental isotopes. It makes up about 1.1% of all natural carbon on Earth.- Detection by mass spectrometry :...

only makes up about 1% of the atomic carbon content of carbon

Carbon

Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

, the rest of the carbon atoms are predominantly NMR inactive ¹²C

Carbon-12

Carbon-12 is the more abundant of the two stable isotopes of the element carbon, accounting for 98.89% of carbon; it contains 6 protons, 6 neutrons, and 6 electrons....

. 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

Carbon-13

Carbon-13 is a natural, stable isotope of carbon and one of the environmental isotopes. It makes up about 1.1% of all natural carbon on Earth.- Detection by mass spectrometry :...

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

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 uniformly thick and well-balanced to ensure that NMR tube...

.

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

NMR

spectrum.

This usually occurs when the purely ¹²C

Carbon-12

Carbon-12 is the more abundant of the two stable isotopes of the element carbon, accounting for 98.89% of carbon; it contains 6 protons, 6 neutrons, and 6 electrons....

compound is symmetrical but where the 1% of the compound which has a ¹³C

Carbon-13

Carbon-13 is a natural, stable isotope of carbon and one of the environmental isotopes. It makes up about 1.1% of all natural carbon on Earth.- Detection by mass spectrometry :...

atom in it is no longer symmetrical.

For example, you can not tell if stilbene

Stilbene

-Stilbene, is a diarylethene, i.e., a hydrocarbon consisting of a trans ethene double bond substituted with a phenyl group on both carbon atoms of the double bond. The name stilbene is derived from the Greek word stilbos, which means shining....

(Ph-CH=CH-Ph) has a cis- or trans- double bond

Double bond

A double bond in chemistry is a chemical bond between two chemical elements involving four bonding electrons instead of the usual two. The most common double bond, that between two carbon atoms, can be found in alkenes. Many types of double bonds between two different elements exist, for example in...

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. 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

NMR spectroscopy

Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy, is a research technique that exploits the magnetic properties of certain atomic nuclei to determine physical and chemical properties of atoms or the molecules in which they are contained...

to the ¹³C atom to give a wide doublet

NMR spectroscopy

. Also, as this molecule is no longer symmetric the ¹³CH= proton will now couple to the adjacent ¹²CH= proton, causing a further doubleting. Thus this additional coupling (additional to the ¹³C coupling) is diagnostic of the type of double bond, and will allow one to determine if the stilbene molecule has a cis- or trans- configuration i.e. by examining the size of the diagnostic J coupling constant

J-coupling

J-coupling is the coupling between two nuclear spins due to the influence of bonding electrons on the magnetic field running between the two nuclei. J-coupling contains information about dihedral angles, which can be estimated using the Karplus equation...

from -CH=CH- bond. Thus only a single 1H NMR spectrum is need, albeit with close inspection of the satellite peaks, rather than any further complex NMR

NMR

or derivative chemical experiments.

The same would be see for 1,2-Dichloroethene

1,2-Dichloroethene

1,2-Dichloroethene, commonly called 1,2-dichloroethylene or 1,2-DCE, is an organochloride with the molecular formula C2H2Cl2. It is a highly flammable, colorless liquid with a sharp, harsh odor. It can exist as either of two geometric isomers, cis-1,2-dichloroethene or trans-1,2-dichloroethene,...

Uses

See also

Further reading