Fragmentation is a type of chemical dissociation

Dissociation (chemistry)

Dissociation in chemistry and biochemistry is a general process in which ionic compounds separate or split into smaller particles, ions, or radicals, usually in a reversible manner...

. Fragmentation of a molecule

Molecule

A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...

 can take place by a process of heterolysis

Heterolysis

In chemistry, heterolysis or heterolytic fission is chemical bond cleavage of a neutral molecule generating a cation and an anion. In this process the two electrons that make up the bond are assigned to the same fragment...

 or homolysis

Homolysis

In general it means breakdown to equal pieces There are separate meanings for the word in chemistry and biology.-Homolysis in chemistry:...

.

It is a phenomenon observed in mass spectrometry

Mass spectrometry

Mass spectrometry is an analytical technique that measures the mass-to-charge ratio of charged particles.It is used for determining masses of particles, for determining the elemental composition of a sample or molecule, and for elucidating the chemical structures of molecules, such as peptides and...

 where it is used as a tool to find the structural formula

Structural formula

The structural formula of a chemical compound is a graphical representation of the molecular structure, showing how the atoms are arranged. The chemical bonding within the molecule is also shown, either explicitly or implicitly...

 of a molecule, process called structural elucidation

Structural elucidation

Structural elucidation is the determination of the chemical structure of chemically uncharacterised substances such as natural products. It is preceded by the extraction and isolation steps. It makes use of various chromatography techniques as well as spectrometric techniques...

.

It can occur in the ion source

Ion source

An ion source is an electro-magnetic device that is used to create charged particles. These are used primarily to form ions for mass spectrometers, optical emission spectrometers, particle accelerators, ion implanters and ion engines.- Electron ionization :...

 (in-source fragmentation) where it is generally not a desired effect. Ion source conformation is an important criterium in the level of fragmentation observed.

Desired fragmentation is made in the collision zone (post-source fragmentation) of a tandem mass spectrometer

Tandem mass spectrometry

Tandem mass spectrometry, also known as MS/MS or MS2, involves multiple steps of mass spectrometry selection, with some form of fragmentation occurring in between the stages.-Tandem MS instruments:...

. It is a part of gas phase ion chemistry

Gas phase ion chemistry

Gas phase ion chemistry is a field of science encompassed within both chemistry and physics. It is the science that studies ions and molecules in the gas phase, most often enabled by some form of mass spectrometry. By far the most important applications for this science is in studying the...

 and there are different types of mass fragmentation:

• collision-induced dissociation
  Collision-induced dissociation
  In Mass spectrometry, Collision-induced dissociation , referred to by some as collisionally activated dissociation , is a mechanism by which to fragment molecular ions in the gas phase. The molecular ions are usually accelerated by some electrical potential to high kinetic energy and then allowed...
  
   (CID),
• electron-capture dissociation (ECD),
• electron-transfer dissociation (ETD)
• electron-detachment dissociation
  Electron-detachment dissociation
  Electron-detachment dissociation is a method for fragmenting anionic species in mass spectrometry....
  
   (EDD),
• photodissociation
  Photodissociation
  Photodissociation, photolysis, or photodecomposition is a chemical reaction in which a chemical compound is broken down by photons. It is defined as the interaction of one or more photons with one target molecule....
  
  , particularly infrared multiphoton dissociation
  Infrared multiphoton dissociation
  Infrared multiphoton dissociation is a technique used in mass spectrometry to fragment molecules in the gas phase usually for structural analysis of the original molecule. -How it works:...
  
   (IRMPD) and blackbody infrared radiative dissociation
  Blackbody infrared radiative dissociation
  In mass spectrometry blackbody infrared radiative dissociation is a method for fragmenting gas phase ions for tandem mass spectrometric analysis . BIRD uses the light from black body radiation to thermally excite the ions until a bond breaks...
  
   (BIRD),
• surface-induced dissociation
  Surface-induced dissociation
  Surface-induced dissociation is a technique used in mass spectrometry to fragment molecular ions in the gas phaseby collision of an ion with a surface under high vacuum....
  
   (SID),
• charge remote fragmentation
  Charge remote fragmentation
  Charge remote fragmentation is a type of covalent bond breaking that occurs in a gas phase ion in which the cleaved bond is not adjacent to the location of the charge. This fragmentation can be observed using tandem mass spectrometry....
  
  ,
• Higher-energy C-trap dissociation
  Higher-energy C-trap dissociation
  Higher-energy collisional dissociation is a fragmentation technique, often used for peptide modification analysis. Immonium ions generated via HCD pinpoint modifications such as phosphotyrosine with very high confidence. An added octopole collision cell facilitates de novo sequencing....
  
   (HCD).

The certain structures favour fragmentation the α-cleavage

Alpha cleavage

Alpha cleavage, ' in organic chemistry, refers to the act of breaking the carbon-carbon bond, adjacent to the carbon bearing a specified functional group.-Mass spectrometry:...

 and the McLafferty rearrangement

McLafferty rearrangement

The McLafferty rearrangement is a reaction observed in mass spectrometry. It is sometimes found that a molecule containing a keto-group undergoes β-cleavage, with the gain of the γ-hydrogen atom...

are two examples for the often observed fragmentations.

External links

• Fragmentation patterns in the mass spectra of organic compounds