2-Octanol, boiling points

The relationship between the molecular structure of an aroma compound and its threshold is still unclear. Volatility of a compound may not relate to its threshold. For example, the threshold of ethanol (boiling point is 78°C) is much higher than octanol (boiling point is 195°C) or other homologous alcohol. Ethanol has high volatility but low odor intensity. It is often used as a solvent in compounded flavors. 

An overview of some basic mathematical techniques for data correlation is to be found herein together with background on several types of physical property correlating techniques and a road map for the use of selected methods. Methods are presented for the correlation of observed experimental data to physical properties such as critical properties, normal boiling point, molar volume, vapor pressure, heats of vaporization and fusion, heat capacity, surface tension, viscosity, thermal conductivity, acentric factor, flammability limits, enthalpy of formation, Gibbs energy, entropy, activity coefficients, Henry s constant, octanol—water partition coefficients, diffusion coefficients, virial coefficients, chemical reactivity, and toxicological parameters. 

Many groups have discussed the correlation between solubility and molecular properties [14-19], and the octanol/water partition coefficient, the molecular volume and surface area, the boiling point and charge distribution in the molecules are well-documented molecular descriptors that correlate strongly with experimental solubility. 

You ve found all the leaks and the pressure in your vacuum distillation setup is, say, 25 torr. Now you need to know the boiling point of your compound, 1-octanol, this time at 25 torr and not 760 torr. You realize it ll boil at a lower temperature, but just how low The handy nomographs in (Figs. 76 and 77) can help you estimate the new boiling point. 

Now suppose you looked up the boiling point of 1-octanol and all you found was 9819. This means that the boiling point of 1-octanol is 98° C at 19 torr. Two things should strike you. 

Now we have a case of having an observed boiling point at a pressure that is not 760 torr (1-octanol again 98°C at 19 torr). We d like to get to 25 torr, our working pressure. This requires a double conversion. 

Basak, S. C., Gute, B. D., and Grunwald, G. D. A comparative study of topological and geometrical parameters in estimating normal boiling point and octanol-water partition coefficient. J. Chem. Inf. Comput. Sci. 1996, 36, 1054—1060. 

In the interest of conserving space in this handbook, a compact tabular presentation format has been adopted. Table 5.1.5.1 lists the chemical name, and its freon number (if applicable), molecular formula, molar weight and melting and boiling points. These data are available for virtually all substances in this group. Also shown in this table is the availability, expressed as a tick mark, of data on vapor pressure, solubility in water, octanol-water partition coefficient (Kqw) and the second order reaction rate constant with hydroxyl radicals. This rate constant is the critical determinant of persistence in the atmosphere. Tables 5.1.5.2 to Table 5.1.5.5 list the compounds and give the available property data with citations. 

Generic chemical class data are often relevant to assessing potential toxicity and should be a part of any evaluation. The relevant information includes structure-activity relationships and physical-chemical properties, such as melting point, boiling point, solubility, and octanol-water partition coefficient. Physical-chemical properties affect an agent s absorption, tissue distribution, biotransformation, and degradation in the body. 

Regarding the latter systems, even better predictions are provided by an empirical parameter the logarithm of the n-octanol-water partition coefficient, log P [66. Another useful empirical retention predictor appears occasionally to be the boiling point, 7], e.g., in the GC of straight and branched bromoalkanes 67j. 

Autoignition temperature 955°C Boiling point 141.1°C Dissociation constant pK = 4.874 Flash point 52-58°C (open cup) Melting point —21.5°C Partition coefficients Octanol water Refractive index = 1.3848 = 0.33. 

Hydrophobicity, from the greek hydro water and phobia aversion, is a term referring to the way a molecule likes or does not like water. A compound with a high hydrophobicity will not be water soluble. It is ap-olar. Conversely, a compound with a low hydrophobicity is said to be hydrophilic or polar. It is likely to be water soluble. In between the two extremes, the hydrophobicity varies. A scale is needed. The problem is that the hydrophobicity, or the polarity of a compound, depends on several parameters such as the dipole moment, the dielectric constant, the polarizability, the proton donor or acceptor character, or even the boiling point to molecular mass ratio. Since the end of the nineteenth century, the octanol-water partition coefficient, P i, was used with success as a measure of hydrophobicity. The log is the convenient scale. Compounds with a positive log Po/w value are more and more hydrophobic or apolar as the value increases. Compounds with a negative log value are hydrophilic or polar [1]. 

Basak, S.C., Gute, B.D. and Grunwald, G.D. (1996a). A Comparative Study of Topological and Geometrical Parameters in Estimating Normal Boiling Point and Octanol/Water Partition Coefficient. J.Chem.Inf.Comput.ScL, 36,1054—1060. 

Anthracene is a solid white to yellow crystal, has a weak aromatic odor, and sinks in water. Its characteristics are boiling point, 342°C melting point, 218°C molecular weight, 178.22 density/specific gravity, 1.25 at 27 and 4°C octanol-water coefficient, 4.45. It is soluble in absolute alcohol and organic solvents. Maximum absorption occurs at 218 nm. 

A further OECD Council Decision in 1991 focused on HPV chemicals. These decisions prompted the development of a minimum hazard data set to describe an HPV chemical - the Screening Information Data Set, or SIDS. This includes physicochemical properties (melting point, boiling point, vapor pressure, water solubility, and octanol-water partition coefficient) environmental fate (stability in water, photodegradation, biodegradation, and an estimate of distribution/transport in the environment) environmental effects (acute toxicity to aquatic vertebrates, invertebrates, and plants) and human health effects (acute toxicity, repeated-dose toxicity, toxicity to the gene and the chromosome, and reproductive and developmental toxicity). 

Physical - chemical QSAR models are available to predict a range of chemical properties including melting point, boiling point, water solubility, biodegradability, vapor pressure, Henry s law constant, sediment adsorptivity, octanol-water partition coefficient, and half-life in the environment. These and other parameters can be readily predicted by EPISUITE (see Relevant Websites section), and enables batch data entry based on Chemical Abstract Service (CAS) numbers or SMILES notations. 

Figure 9.1 Number of publications dealing with physicochemical properties as keywords in environmental sciences, pharmacology and pharmacy, and medicinal chemistry. The following combinations of words water/aqueous solubility, logP/lipophilicity, octanol/water, vapor/vapour pressure, melting point, boiling point were searched in the topic category of ISI Web of knowledge (http //www.isiknowledge.com).

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