Molecular weight determining formula from

We recall from Chapter 10 that the percentages of the elements in a compound can be used to compute the simplest formula for the compound. When the substance is soluble in some suitable liquid, we can combine the empirical formula with a molecular-weight determination by freezing-point depression to get the true formula. 

Molecular Weight Determine the Hydroxyl Value, H, from the above test, and calculate the molecular weight by the formula... 

K. Determine the molecular weight of sucrose from these data, and discuss the reason for any discrepancies compared to the molecular weight as calculated from the formula for sucrose. 

One of the most important reactions of diborane is its interaction with amalgams of highly active metals, e.g. sodium and potassium, to give compounds such as KgBgHg, which are sometimes referred to as salts of diborane. These compounds are non-volatile, insoluble in liquid ammonia and common organic solvents and react with water. Consequently their formulae have been determined from magnetic measurements and not from molecular weight determinations. The addition of two electrons to the electronically unsaturated diborane,... 

Determine molecular weights and formulas of gaseous substances from measured properties of gases... 

The deep-yellow base serpentinine, first isolated from Rauwolfia serpentina Benth. ex Kurz and later from other related species, possesses the molecular formula C42H44O6N4, based on elemental analyses and molecular weight determinations. The anhydrous compound is hygroscopic and crystallises with 1—2 moles of water. The analyses of a number of salts agree with this formula. 

Why is this number the molecular weight of sugar (5) Calculate the theoretical molecular weight of sugar from its formula which is CigHggOn. (6) What was the percentage error in your determination ... 

Coordinately saturated polymers of composition (H2NBH2) are identified but not characterized. They are amorphous materials and their polymerization degree is believed to be quite low ( 15.2.5.3). A polymer of the same formula unit is prepared from pyrolysis of NH3BH3 under a low pressure of nitrogen. This polymer lacks sufficient solubility for molecular weight determination but is crystalline, in contrast to the materials of the same composition reported earlier, and its x-ray diffraction pattern differs from that of any known cyclic boranamine. 

The student has already seen, in a number of cases, how the structure of a substance is derived from a study of its reactions But in most of the cases which have been described, the structural formula has been given, and it has been shown that the reactions of the substance are in accord with the formula. It is easier to see the relations between structure and reactions from this point of view, and, consequently, this method has been adopted up to the present. In determining the structure of a new substance, the investigator has before him only the results of analyses and molecular weight determinations of the new compound and the derivatives which he has prepared from... 

From this relative area calculation, we can state that there are twice as many protons in the group giving rise to peak B as there are in the group giving rise to peak C and that there are 3 x as many protons in the peak A group as in the peak C group. We cannot say that peak C is due to one proton and peak A due to three protons without more information. The empirical formula can be determined if we have elemental analyses information and the molecular formula can be calculated if the molecular weight is known from another measurement, such as MS. 

The authors [226] constructed the dependence x MM) in double logarithmic coordinates for PS-Cgg solutions in two solvents— tetrahydro-fliran and chloroform. These dependences proved to be linear, that allows to estimate the exponent for the studied polymers, which proved to be equal to -0.06 0.07 for tetrahydrofuran and 0.2 0.2—for chloroform. However, this construction causes a questions number. Firstly, in the well-known Mark-Kuhn-Houwink equation (the formula (1)) coefficientdepends on both exponent and macromolecular repeated link molecular weight m. One from the relationship between K, and variants is the Eq. (2). The plots v MM) in double logarithmic coordinates construction and subsequent the exponent determination from their slope assumes the condition K =const, that is not far from obvious. 

Jorgensen from 1877 used similar formulae but regarded chains of 4NH3 molecules as stable arrangements (II). After Nikon and Pettersson, and J. Petersen, showed by molecular weight determinations that these formulae must be halved, they were written as in HI. Such formulae could explain why part of the chlorine (directly linked to the metal) is not precipitated by silver nitrate, and also the existence of isomers. Such, in brief, was the state of knowledge when Werner approached the subject. 

I One of the first steps in determining molecular structure is establishing the molecular formula. In the past, this task was most commonly done by elemental analysis, combustion analysis to determine percent composition, molecular weight determination, and so forth. More commonly today, molecular weight and molecular formula are determined by mass spectrometry (Chapter 14). In the examples that follow, we assume that the molecular formula of any unknown compound has already been determined, and we proceed from that point using spectral analysis to determine a structural formula. 

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