Polar portion

C12-0071. An aqueous solution contains 1.00 g/L of a derivative of the detergent lauryl alcohol. The osmotic pressure of this solution at 25.0 °C is measured to be 64.8 torr. (a) What is the molar mass of the detergent (b) The hydrocarbon portion of the molecule is an 11-carbon chain. What is the molar mass of the polar portion ... 

Fig. 7 Diagrammatic representation of the fluid mosaic model of the cell membrane. The basic structure of the membrane is that of a lipid bilayer in which the lipid portion (long tails) points inward and the polar portion (round head ) points outward. The membrane is penenetrated by transmembrane (or integral) proteins. Attached to the surface of the membrane are peripheral proteins (inner surface) and carbohydrates that bind to lipid and protein molecules (outer surface). (Modified from Ref. 14.)...

Surface active agents, more commonly known as surfactants, are the groups of chemical compounds that in the most common form constitute an ionic or polar portion (hydrophilic head) and a hydrocarbon portion (hydrophobic tail). The ionic or polar portion interacts strongly with the water via dipole-dipole or ion-dipole interactions and... 

A surfactant is a molecule that is characterized as amphiphilic, i.e., containing both a discrete hydrophilic (water-soluble) or polar portion and a well-defined hydrophobic (oil-soluble) or nonpolar fragment. The hydrophilic portion of the molecule is called the surfactant headgroup the hydrophobic portion of a surfac-... 

In a similar fashion the bonding in H2 might be formally regarded as a complementary pair of one-electron donor-acceptor interactions, one in the ot (spin up ) and the other in the 3 (spin down ) spin set.8 In the long-range diradical or spin-polarized portion of the potential-energy curve, the electrons of ot and (3 spin are localized on opposite atoms (say, at on HA and 3 on HB), in accordance with the asymptotic dissociation into neutral atoms. However as R diminishes, the ot electron begins to delocalize into the vacant lsB(a) spin-orbital on HB, while (3 simultaneously delocalizes into Isa on HA, until the ot and (3 occupancies on each atom become equalized near R = 1.4 A, as shown in Fig. 3.3. These one-electron delocalizations are formally very similar to the two-electron ( dative ) delocalizations discussed in Chapter 2, and they culminate as before (cf. Fig. 2.9) in an ionic-covalent transition to a completely delocalized two-center spin distribution at... 

A structure formed by the reversible association of am-phiphiles in apolar solvents. In inverted micelles, the polar portion of the amphiphile is concentrated in the interior of the macrostructure. Such association usually occurs with aggregation and is not typically characterized by a definite nucleation stage. Thus, inverted micelles (also referred to as inverse or reverse micelles) often fail to exhibit critical micelle concentration behavior. See Micelle... 

It has already been observed in the case of pure liquids such as substituted hydrocarbons that the surface tension was, if not completely defined by the non-polar portions of the molecule, at least not so markedly affected by substituent groups as we should anticipate if no orientation existed. Again, although vaporisation and condensation at a liquid surface such as water at high temperatures takes place with great speed, yet the life of a molecule on the surface is probably long enough to permit of such adjustment as orientation requires. Even more conclusive in favour of the hjq)othesis of at least partial orientation is the evidence derived from a consideration of the latent heats of evaporation and the... 

Thus the type of emulsion formed depends essentially on the relative cross-section areas of the non-polar and polar portions of... 

Each surfactant molecule includes a hydrophobic, nonpolar portion, and a hydrophilic, polar portion. The polar portion is either nonionic (neutral), anionic (negatively charged), or cationic (positively charged). For more information on surfactants see T0759, Surfactants—General. 

Since the polar groups repel each other, the expanded random coil molecules tend to become stiff rods. The nonpolar portions of the water-solubilized polymer face toward the organic phase at the organic-aqueous interfaces, and the polar portions preferentially point away from the organic phase. 

Since the phospholipids have cis-unsaturated fatty acid components there is a certain amount of fluidity to the bilayer. You can picture a sea of lipids moving in a transverse motion across the inside and outside faces. Note that the exterior of the membrane is composed of the polar portions of the biolipids while the interior of the membrane is highly nonpolar. 

In another related study (using hexadecyltrimethyl ammonium bromide micelles), isopropyl benzene was solubilized, and the chemical shifts of aromatic and alkyl protons were observed. The results suggest that the isopropyl benzene molecules are oriented such that the isopropyl groups are buried more deeply in the core of the micelle, while the benzene ring is in the more hydrated palisade layer. This plus the conclusion of Item 3 is consistent with the description presented in Section 8.3, which located the benzene in a relatively polar portion of the micelle. 

The structures of the various lipoproteins appear to be similar (figs. 20.11 and 20.12). Each of the lipoprotein classes contains a neutral lipid core composed of triacylglycerol and/or cholesteryl ester. Around this core is a coat of protein, phospholipid, and cholesterol, with the polar portions oriented toward the surface of the lipoprotein and the hydro-phobic parts associated with the neutral lipid core. The hydrophilic surface interacts with water in plasma, promoting the solubility of the lipoprotein. 

In this study, partial atomic charges were used as predictors to represent the effects of the polar portion of cohesive and adhesive energies. In this approach, a molecule was arbitrarily divided into polar and nonpolar parts on the basis of the elements constituting the chemical structure of the molecule. The polar portion of a molecule consisted of the following two classes of elements ... 

By means of ion bombardment and the concurrent UV radiation, functional groups on the surface of the substrate are activated. This increases the polar portion of the surface energy, thereby improving the adhesion of the evaporated layer to the substrate (Fig. 8.4) [5]. 

Fig. 8.4. Adhesion in the polar portion of the surface energy as a result of plasma treatment by BOPP [7].

From the polar portion of the methanolic extract of the fruit of anise (P. anisum L.), Fujimatu et al. (2003) isolated aromatic compound glucosides and an alkyl glucoside. 

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