Order of addition

The stmcture of individual block polymers is deterrnined by the nature of the initiator (1,2-propanediol above), the sequence of addition of propylene and ethylene oxides, and the percentage of propylene and ethylene oxides in the surfactant. Thus, when the order of addition is reversed, a different stmcture is obtained in which the hydrophobic moieties are on the outside of the molecule. With ethylene glycol as the initiator, the reactions are as foUows ... 

The living polymerization process offers enormous flexibiUty in the design of polymers (40). It is possible to control terminal functional groups, pendant groups, monomer sequencing along the main chain (including the order of addition and blockiness), steric stmcture, and spatial shape. 

The physical characteristics of a fat or oil for imitation dairy products are not necessarily dictated by the fat being replaced, but by the composition, processiag methods, and conditions of use of the substitute product. Thus, the selection of the fat or oil is generally developed experimentally. The chemical and physical nature of the components of the system, order of addition, shear iaput, and processiag temperature dictate the final iateractions and the nature of the product. A comparison of the characteristics of milk fat and three different fats that are used ia satisfactory filled and imitation milks are listed ia Table 1 and those that comprise whipped toppiag, ia Table 2. 

For moderate ratios (<3), the type of emulsion is decided by several factors (5), such as order of addition or type of emulsifier. One Hquid slowly added to the other with agitation usually results in the last-mentioned phase being the continuous one. Another factor is preferred solubiHty of the emulsifier the phase in which the emulsifier is soluble most probably is continuous. 

When chloral was usedasthealdehyde2equivalents reacted with 1 equivalent of the enamine (98) regardless of the ratio of reactants or order of addition to give 2,6-bis(trichloromethyl)-5,5-dimethyl-4-morpholino-/ i-dioxane (183) in 83 % yield (126). Hydrolysis of 183 with hydrochloric acid at room temperature gave the hemiaeetal (184), but when heated with acid, the aldol product (185) was formed. 

In addition to its other properties, interest in the potential use of the vasodilative properties of prostaglandin El, alprostadil ( ), has led to several conceptually different syntheses.For this purpose, the classic Corey process has to be modified by reversing the order of addition of the side chains to allow for convenient removal of the unwanted double bond in the upper side chain. For example, Corey lactone is protected with dihydropyran (acid catalysis), reduced to the lactol with diisobutyaluminum hydride, and then subjected to the usual Wittig reaction to give intermediate This is... 

Caution The order of addition must be observed in this procedure or inflammation may occur. 

Oil-base mud maintenance involves close monitoring of the mud properties along with the mud temperature, as well as the chemical treatment (in which the order of additions must be strictly followed). The following general guidelines should be considered ... 

The transfer of an ethyl group, in particular, can be performed with high diastereoselectivity by the use of tetraalkyllead, activated with titanium(IV) chloride14"15 (Table 4). The order of addition of the reagents exhibits a strong influence on the chemical yield and diastercoselectiv-ity of the addition reaction. Typically, titanium(IV) chloride is added at -78CC to the aldehyde, followed by addition of tetraethyllead. Poor yields and diastereoselectivity are observed if titanium(IV) chloride is first added to tetraethyllead followed by addition of the aldehyde ... 

Isopropyl alcohol (IPA) or benzyl alcohol (toluol) often are used in the formulation (as early components in the order of addition) to dissolve the surfactant-detergent base [e.g., Duomeen OL (Akzo Nobel Chemicals, Inc.) or Triton N101 (Union Carbide Corp.)]. 

While inference has been made in a few cases as to the order of addition of ligands in prethermal reactions, no generalization can yet be made. When only one type of ligand is present, it is clear that the same ligand type may... 

After the addition of the non-radioactive material, the labeled material is added to the mixture and the mixture allowed to proceed toward equilibriim. In equilibrium analysis the order of addition of reagents is not critical as long as sufficient time is allowed for establishing equilibrium of the complete mixture (3,4). 

Dispersion instability can result from an order of addition which creates a... 

Experimental protocol is built into the construction of tree diagrams so that intermediates that are isolated are distinguishable from those that are made in situ, and the order of input dots matches the order of addition of reagents used in the synthesis plan. 

It is essential that the temperature of the first step not exceed 35 °C to minimize undesirable decomposition of the 4-alkoxydiphenylamines. In addition, the 4-alkoxydiphenylamines should be added to a solution of the keto acids in sulfuric acid. The reverse order of addition does not produce good results, because the 4-alkoxydiphenylamines are liable to decompose in sulfuric acid even at lower temperature. On the other hand, the phthalides are stable to a considerable extent in sulfuric acid at 35°C or below. The reaction is substantially completed in a few hours after dissolution of the 4-alkoxydiphenylamines. The second step proceeds easily at 50 °C or higher, and sodium hydroxide is successfully employed as base, though any base can be used. 

Variables in the condensation reaction include the temperature, nature of the solvent, order of addition (either chlorosilane to excess sodium or "inverse" addition, sodium to excess chlorosilane), and the rate of addition. A careful study of reaction variables by the Sandia group of Dr. John Zeigler(15) will be described in detail elsewhere in this volume. 

Phase inversion along the dilution path (by addition of water to the oil/surfactant mixture) followed for nanoemulsion preparation was confirmed by conductivity measurements, and was found to be essential for obtaining finely dispersed systems, as transparent dispersions were not obtained if the order of addition of the components was changed following an experimental path with no phase inversion (Figure 6.2). 

The reverse order of addition lowers the yield to 50 per cent. 

Polymerizations. The polymerizations were carried out in an argon atmosphere in capped glass bottles fitted with a neoprene rubber gasket inner liner. In charging the polymerizations, the order of addition of materials was solvent first, then metal alkyls, next the barium salt, and finally the monomer(s). The amount of metal alkyl charged was sufficient to titrate the acidic impurities present in the solvent and polymerization bottle, plus the calculated amount for initiation of polymerizations. The mole ratio of barium to metal alkyl(s) was based on the moles of total alkalinity of barium to the moles of carbon-metal assayed. Unless otherwise stated,... 

Block copolymers of /3-PL and /3-BL have been synthesized using (251), although reaction times of several weeks are required.782 Since (TPP)Al-based carboxylates are also known to polymerize epoxides (see Section 9.1.7.2), the sequential addition of /3-BL and propylene oxide (PO) results in formation of a p(/3-BL-/3-PO) diblock.782 However, reversing the order of addition fails to produce the block copolymer since the propagating alkoxide (TPP)Al(OCHMeCH2)nCl does not initiate the ROP of /3-BL. 

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