The Rule of Thirteen

To comprehend how the Rule of Thirteen might be applied, consider an unknown substanee with a molecular mass of 94 amu. Application of the formula provides... [Pg.8]

Calculate the molecular formulas for possible compounds with molecular masses of 136, using the Rule of Thirteen. You may assume that the only other atoms present in each molecule are carbon and hydrogen. [Pg.12]

A carbohydrate was isolated from a sample of cow s milk. The substance was found to have a molecular mass of 342. The unknown carbohydrate can be hydrolyzed to form two isomeric compounds, each with a molecular mass of 180. Using the Rule of Thirteen, determine a molecular formula and an index of hydrogen deficiency for the unknown and for the hydrolysis products. Hint Begin by solving the molecular formula for the 180-amu hydrolysis products. These products have one oxygen atom for every carbon atom in the molecular formula. The unknown is lactose. Look up its structure in The Merck Index and confirm its molecular formula.)... [Pg.12]

Assign a structure that would be expected to give rise to each of the following mass spectra. Note Some of these problems may have more than one reasonable answer. In some cases, infrared spectral data have been included in order to make the solution to the problems more reasonable. We recommend that you review the index of hydrogen deficiency (Section 1.4) and the Rule of Thirteen (Section 1.5) and apply those methods to each of the following problems. To help you, we have provided an example problem with solution. [Pg.449]

The molecular ion appears at an mie value of 134. Applying the Rule of Thirteen gives the following possible molecular formulas ... [Pg.449]

Notice that the NMR shows a total of five peaks, corresponding exactly to the number of carbons in the molecular formula This is a nice check on our calculation of the formula via the Rule of Thirteen (five earbon atoms). The peak at 174 ppm corresponds to the ester C=0 carbon. The peak at 60 ppm is a deshielded earbon atom eaused by a neighboring single-bonded oxygen atom. The rest of the earbon atoms are relatively shielded. These three peaks eorrespond to the remaining part of the carbon chain in the ester. [Pg.469]

As a first step in the Rule of Thirteen, we generate a base formula, which contains only carbon and hydrogen. The base formula is found by dividing the molecular mass M by 13 (the mass of one carbon plus one hydrogen). This calculation provides a numerator n and a remainder r. [Pg.9]

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