(4S)-limonene synthase

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The Hildebrand solubility parameter (δ) provides a numerical estimate of the degree of interaction between materials, and can be a good indication of solubility, particularly for non polar materials such as many polymers. Materials with similar values of δ are likely to be miscible.

Definition

The Hildebrand solubility parameter is the square root of the cohesive energy density:

δ=ΔHvRTVm

The cohesive energy density is the amount of energy needed to completely remove unit volume of molecules from their neighbours to infinite separation (an ideal gas), which is equal to the heat of vaporization divided by molar volume. In order for a material to dissolve, these same interactions need to be overcome as the molecules are separated from each other and surrounded by the solvent. Dr. Joel Henry Hildebrand suggested the square root of the cohesive energy density as a numerical value indicating solvency behavior. This later became known as the “Hildebrand solubility parameter”. Materials with similar solubility parameters will be able to interact with each other, resulting in solvation, miscibility or swelling.

Uses and Limitations

Its principal utility is that it provides simple predictions of phase equilibrium based on a single parameter that is readily obtained for most materials. These predictions are often useful for non-polar and slightly polar (dipole moment <2 debyesPotter or Ceramic Artist Truman Bedell from Rexton, has interests which include ceramics, best property developers in singapore developers in singapore and scrabble. Was especially enthused after visiting Alejandro de Humboldt National Park.) systems without hydrogen bonding. It has found particular use in predicting solubility and swelling of polymers by solvents. More complicated 3 dimensional solubility parameters, such as Hansen Solubility Parameters, have been proposed for polar molecules.

The principal limitation of the solubility parameter approach is that it applies only to associated solutions ("like dissolves like" or, technically speaking, positive deviations from Raoult's law): it cannot account for negative deviations from Raoult's law that result from effects such as solvation or the formation of electron donor acceptor complexes. Like any simple, predictive theory it can inspire overconfidence: it is best used for screening with data used to verify the predictions.

Units

The conventional units for the solubility parameter are (calories per cm3)1/2, or cal1/2 cm-3/2. The SI units are J1/2 m-3/2, equivalent to the pascal1/2. 1 calorie is equal to 4.184 J.

1 cal1/2 cm-3/2 = (4.184 J)1/2 (0.01 m)-3/2 = 2.045 × 103 Pa1/2

Given the non-exact nature of the use of δ, it is often sufficient to say the number of MPa1/2 is twice the number of (cal1/2 cm-3/2). Where the units are not given, for example in older books, it is usually safe to assume the non SI unit.

Examples

Substance δ[1] [cal1/2 cm-3/2] δ [MPa1/2]
n-Pentane 7.0 14.4
n-hexane 7.24 14.9
Diethyl Ether 7.62 15.4
Ethyl Acetate 9.1 18.2
Chloroform 9.21 18.7
Dichloromethane 9.93 20.2
Acetone 9.77 19.7
2-propanol 11.6 23.8
Ethanol 12.92 26.2
PTFE 6.2[2]
Poly(ethylene) 7.9[2]
Poly(propylene) 8.2[3] 16.6
Poly(styrene) 9.13[2]
Poly(phenylene oxide) 9.15[2]
PVC 9.5[3] 19.5
PET 10.1[3] 20.5
Nylon 6,6 13.7[3] 28
Poly(methyl methacrylate) 9.3[3] 19.0
(Hydroxyethyl)methacrylate 25-26[4]
poly(HEMA) 26.93[4]
Ethylene Glycol 29.9[3][4]

From the table, poly(ethylene) has a solubility parameter of 7.9 cal1/2 cm-3/2. Good solvents are likely to be diethyl ether and hexane. (However, PE only dissolves at temperatures well above 100°C.) Poly(styrene) has a solubility parameter of 9.1 cal1/2 cm-3/2 , and thus ethyl acetate is likely to be a good solvent. Nylon 6,6 has a solubility parameter of 13.7 cal1/2 cm-3/2, and ethanol is likely to be the best solvent of those tabulated. However, the latter is polar, and thus we should be very cautions about using just the Hildebrand solubility parameter to make predictions.

See also

References

Notes

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Bibliography

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20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.

My blog: http://www.primaboinca.com/view_profile.php?userid=5889534

External links

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    A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running

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