Number of double-bond equivalencies

In this book, in order that you can concentrate your attention on the NMR spectra, we shall provide you with the molecular formula in all cases. This in turn provides you with information which can be extremely useful during the process of solving the structure if the molecule only contains C, H, N and O then you can use the molecular formula to obtain the number of so-called double bond equivalents, i.e. information on the degree of unsaturation. Though there are various formulas which can be devised to do this, we recommend the calculation using the following formula for a molecule CaHbOcNd, the number of double bond equivalents DBE is calculated as follows... 

First use the molecular formula and the equation given above to calculate the number of double bond equivalents. In this case (remembering to treat bromine as equivalent to hydrogen) the value is 1. The infrared spectrum shows a band at 1641 cm 1, which probably represents the C=C bond stretch, but in this case there can only be a C=C bond present ... 

Index of Hydrogen Deficiency (degree of unsaturation, the number of double-bond equivalence) ... 

FIGURE 7.4 The PCA score plot of mass spectral data from ketones shows clustering by the number of double bond equivalents (indicated by the numbers 1-5). Variables used are 14 autoscaled modulo-14 features. 

Build search criteria that include information such as possible elements and the numbers of each element maximum and minimum number of double bond equivalency (DBE) maximum tolerance of experimental error in the determined exact mass. 

Calculate the number of double bond equivalents in a molecule from its formula... 

For a neutral species, we can calculate the number of double bond equivalents, DBE (Q), by comparing the molecular formula with that of the fully saturated, acyclic parent molecule with the same number of carbons and heteroaloms, C H 2 +2+yN. O ., where H is the total number of hydrogens and halogens. 

Q The local anaesthetic benzocaine has a molecular formula of C9H11NO2. (a) Calculate the number of double bond equivalents (b) identify all of the double bond equivalents in benzocaine (1.2),... 

The number of double bond equivalents corresponds to the difference between the molecular formula and that for the saturated acyclic parent compound. Each DBE (double bond or ring) results in the subtraction of 2 hydrogens or halogens from the molecular formula of this parent structure. 

A Knowing the molecular formula of A we recommend that the first step should be to calculate the number of double bond equivalents in the molecule, using equation (1.3), and then to use this as an indication of the number of functional groups present ... 

For an organic compound the first step is usually to find the molecular formula, probably from the mass spectrum, and to calculate the number of double bond equivalents (DBEs). An acyclic saturated hydrocarbon has the formula where M = 2N+2. Each double bond or ring in the molecule reduces the value of M by two. So if M = 2N the molecule has one DBE we cannot tell from the formula whether it is in the form of a ring or unsaturation. A benzene ring corresponds to 4 DBEs three double bonds and a ring. The presence of oxygen or other divalent elements does not affect the value of M. Each monovalent atom such as chlorine can be treated as a proton for the purpose of calculation, while one proton has to be subtracted for each trivalent atom such as nitrogen. 

Knowing the number of double bond equivalents for a formula derived by high-resolution mass spectrometry is a quick short cut to generating some plausible structures. You can then rule them in or rule them out by comparing with IR and NMR data. 

Some organic chemists refer to the index of hydrogen deficiency as the degree of unsaturation or the number of double-bond equivalencies. ... 

In Subsection 8.8.1 we defined criteria to test for the existence of molecular formulas, based on the sum of atom valencies. This concept is also known as the number of double bond equivalents. For a molecular formula p the number of double bond equivalents is defined as... 

Calculation of the Number of Double Bond Equivalents from the Molecular Formula... 

For compounds containing only C, H, O, N, S, and halogens, the following steps permit a quick and simple calculation of the number of double bond equivalents ... 

The next important question to answer is does the unknown molecule eontain any double bonds, triple bonds, or rings We can answer this question by examining the molecular formula and working out the number of double-bond equivalents in the molecule. A saturated acyclic (non-cyclic) hydrocarbon has a molecular formula... 

If we set n equal to 3 and ignore the oxygen, then the saturated compound would be C3Hg, so the number of double-bond equivalents is one, that is,... 

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