Molecular Weight of Organics

The chief methods available for the determination of the molecular weight of organic compounds are ... 

Where M is the molecular weight of the solute, Dt is the elevation of boiling point in °C, c is the concentration of solute in grams for lOOOgm of solvent, and K is the Ebullioscopic Constant (molecular elevation of the boiling point) for the solvent. K is a fixed property (constant) for the particular solvent. This has been very useful for the determination of the molecular weights of organic substances in solution. 

A very elegant and simple method by which the molecular weight of organic substances can be determined in a melting point apparatus was recently described by K. East.1... 

Rast method analy chem The melting-point depression method often used for the determination of the molecular weight of organic compounds. rast. meth-od rate constant physchem Numerical constant in a rate-of-reaction equation for example, = feCaACbBCcC, where and Cc are reactant concentrations, k is the... 

THE SEPARATION, PURIFICATION, IDENTIFICATION, ANALYSIS AND DETERMINATION OF THE MOLECULAR WEIGHT OF ORGANIC COMPOUNDS... 

A brief discussion of the separation, purification, identification, analysis and determination of molecular weight of organic compounds is given in an appendix instead of in an introductory chapter as is customary. In the presentation of the above topics, which belong more especially to a laboratory guide, only general methods are given without anj of the details that must be observed in each case. 

This is a classical method for measurement of molecular weights of organic compounds. Calculation of the freezing-point depression proceeds exactly... 

Wheeler, J.R., 1976. Fractionation by molecular weight of organic substances in Georgia coastal waters. Limnol. Oceanogr., 21 846—852. 

Qualitative analysis MS can be used to identify the molecular weight of organic and inorganic compounds, from very small molecules to large polymers and biological molecules (> 100,000 Da). MS is a powerful tool in the determination of the structure of organic compounds. Fragmentation patterns can reveal the presence of substructure units within the molecule. 

As the molecular weight of organic compoimds increases, so their tendency to be present in airborne particles rather than within the vapor phase increases. Very important groups of substances, such as the polycychc aromatic hydrocarbons and the chlorinated dibenzo-/7-dioxins/furans, ate termed semivolatile since they exist in the atmosphere in partition between particle and vapor phases. Measurements of emissions also need to account for both physical forms. 

D. Scott. Rapid and accurate method for estimating molecular weights of organic compounds from low-resolution mass spectra. Chemometr. Intell. Lab. Syst, 16(3) 193-202,1992. 

High-resolution mass spectrometers are capable of recording mje values down to several decimal places, and the intensity of the peaks with an accuracy of fractions of 1%. This allows one to carry out elegant, though by no means straightforward, determinations of the elementary analysis and molecular weight of organic compounds. 

Camphor is a white solid that melts at 179.5°C. It has been used to determine the molecular weights of organic compounds, because of its unusually large... 

Raoult, Francois-Marie (1830-1901) A French chemist who studied the behaviour of solutions and their physical properties. He is best known for his work on solutions, in particular the depression of freezing points and the depression of a solvent s vapour pressure due to a solute that was shown to be proportional to the solute s molecular weight. Both became ways of determining molecular weights of organic substances. "Raoult s law is named after him. 

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