Kendrick mass
Encyclopedia
The Kendrick mass is a mass obtained by multiplying the measured mass by a numeric factor. The Kendrick mass is used to aid in the identification of molecules of similar chemical structure from peaks in mass spectra. The method of stating mass was suggested in 1963 by the chemist
Edward Kendrick.
To convert an IUPAC mass to the Kendrick mass, the equation
is used. The mass in dalton units (Da) can be converted to the Kendrick scale by dividing by 1.0011178.
Other groups of atoms in addition to CH2 can be used to obtain the Kendrick mass, for example COO, H2, H2O, and O. In this case, the Kendrick mass for a family of compounds F is given by
.
For hydrocarbon analysis, F=CH2.
A recent publication has suggested that Kendrick mass be expressed in Kendrick units with symbol Ke.
(integer) Kendrick mass:
The members of an alkylation
series have the same degree of saturation
and number of heteroatoms (nitrogen
, oxygen
and sulfur
) but differ in the number of CH2 units. Members of an alkylation series have the same Kendrick mass defect.
The Kendrick mass defect has also been defined as
.
The abbreviations KM and KMD have been used for Kendrick mass and Kendrick mass defect, respectively. In some definitions, the KMD
A Kendrick mass analysis is often used in conjunction with a Van Krevelen diagram
, a two- or three- dimensional graphical analysis in which the elemental composition of the compounds are plotted according to the atomic ratios H/C, O/C, or N/C.
Chemist
A chemist is a scientist trained in the study of chemistry. Chemists study the composition of matter and its properties such as density and acidity. Chemists carefully describe the properties they study in terms of quantities, with detail on the level of molecules and their component atoms...
Edward Kendrick.
Definition
According to the procedure outlined by Kendrick, the mass of CH2 is defined as 14.000 Da, instead of the IUPAC mass of 14.01565 Da.To convert an IUPAC mass to the Kendrick mass, the equation
-
.
is used. The mass in dalton units (Da) can be converted to the Kendrick scale by dividing by 1.0011178.
Other groups of atoms in addition to CH2 can be used to obtain the Kendrick mass, for example COO, H2, H2O, and O. In this case, the Kendrick mass for a family of compounds F is given by
.For hydrocarbon analysis, F=CH2.
A recent publication has suggested that Kendrick mass be expressed in Kendrick units with symbol Ke.
Kendrick mass defect
The Kendrick mass defect is defined as the exact Kendrick mass subtracted from the nominalNominal mass
The nominal mass is the integer mass of the most abundant naturally occurring stable isotope of an element. The nominal mass of a molecule is the sum of the nominal masses of the elements in its empirical formula.H2O = 18...
(integer) Kendrick mass:
The members of an alkylation
Alkylation
Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion or a carbene . Alkylating agents are widely used in chemistry because the alkyl group is probably the most common group encountered in...
series have the same degree of saturation
Degree of saturation
Degree of saturation may refer to:*Degree of saturation , a ratio of liquid in a porous material *Degree of saturation , a measure used in traffic engineering...
and number of heteroatoms (nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
, oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
and sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
) but differ in the number of CH2 units. Members of an alkylation series have the same Kendrick mass defect.
The Kendrick mass defect has also been defined as
.The abbreviations KM and KMD have been used for Kendrick mass and Kendrick mass defect, respectively. In some definitions, the KMD
Kendrick mass analysis
In a Kendrick mass analysis, the Kendrick mass defect is plotted as function of nominal Kendrick mass for ions observed in a mass spectrum. Ions of the same family, for example the members of an alkylation series, have the same Kendrick mass defect but different nominal Kendrick mass and are positioned along a horizontal line on the plot. If the composition of one ion in the family can be determined, the composition of the other ions can be inferred. Horizontal lines of different Kendrick mass defect correspond to ions of different composition, for example degree of saturation or heteroatom content.A Kendrick mass analysis is often used in conjunction with a Van Krevelen diagram
Van Krevelen diagram
Van Krevelen diagrams are a graphical-statistical method that cross-plots the hydrogen:carbon in function of the oxygen:carbon atomic ratios of carbon compounds. Different kinds of organic matter are more likely to produce oil during thermocatalytic maturation than other types: Algae, type 1,...
, a two- or three- dimensional graphical analysis in which the elemental composition of the compounds are plotted according to the atomic ratios H/C, O/C, or N/C.