Piperazine, physical properties

N1 -acylsulfanilamides, 23 508 A21-heterocyclic derivatives, 23 508 Ar -heterocyclic-Ar -acylsulfanilamides, 23 508 A21-heterocyclic sulfanilamides, 23 507—508 2V-(2-aminoethyl)-l,3-propylenediamine physical properties, 5 486t 2V-(2-aminoethyl)-piperazine (AEP), 5 485 N2 oxidation, Birkeland-Eyde process of, 27 291-292, 316. See also Dinitrogen entries Nitrogen entries N3 -P5 phosphoramidates, 27 630-631 Na+, detection in blood, 24 54. See also Sodium entries Nabarro-Herring creep, 5 626 Nacol 18, chain length and linearity, 2 10t Nacreous pigments, 7 836-837 19 412 Nacrite, 6 659... 

As in the case of nylons, the flexibility of PUs is increased as the number of methylene groups is increased, and the rigidity is related to the number of stiffening groups, such as phenylene groups in the chain. As the number of methylene units increases (Table 14.6), the Tm decreases. The Tm generally increases as the flexible units are replaced by nonflexible units, such as phen-ylenes and piperazines. Thermal and physical properties of aliphatic PUs are shown in Table 14.7. 

This chapter covers the preparations, physical properties, and reactions of pyrazine and its C-alkyl, C-aryl,. V-alkyl, or A/ -aryI derivatives as well as their respective di-, tetra-, and hexahydro derivatives (the last usually known as piperazines). In addition, it includes methods for introducing alkyl or aryl groups (substituted or otherwise) into pyrazines and hydropyrazines already bearing substituents and the reactions specific to the alkyl or aryl groups in such products. For simplicity, the term alkylpyrazine in this chapter is intended to include alkyl-, alkenyl-, alkynyl-, cycloalkyl-, and aralkylpyrazines likewise, the term arylpyrazine includes both aryl- and heteroarylpyrazines. 

Physical properties, 45 Piperazine A JV -dithio-acetamide, condensation, with u)-btomoacetophenones,... 

Although the MDEA/piperazine process can be modelled in a very similar fashion to MDEA-only (Section 2.3) using the ElecNRTL physical property approach in Aspen Plus, the ions of piperazine and their electrolyte reactions in Eqs. (14)-(17) are not contained in the Aspen Properties database. Therefore, the electrolyte wizard cannot be used to add the equations and their components, and instead they must be added in manually. Once the components have been added, the electrolyte reactions can then be manually added in the Chemistry section (be sure to include it in the same chemistry specification which also includes the MDEA electrolyte reactions). Note that newer versions of Aspen Plus now include a simple example for using this setup in the Examples folder (select ElecNRTL Rate Based PZ+MDEA Model.bkp). It is usually easier to start with this file and modify it for your own purposes than it is to enter the data manually. 

Others have taken different approaches for greater accuracy or the use of industrial data. Custom molecules can be created in Aspen Properties, along with corresponding physical property parameters and models, and custom electrolyte reactions can be entered in the Chemistry section and all of the associated equilibrium constant models. For more information on this approach, see Mudhasakul et al. [10], who developed an Aspen Properties package for this system. Alternative strategies include developing custom models in Aspen Custom Modeller for the different units of operation using simplified forms of the piperazine interaction equations [26]. 

The perhydropyrazine (piperazine) heterocycle has been a favorite of the polymer chemist for the preparation of both addition and condensation polymers because of the desirable physical and chemical properties imparted by the ring. Piperazine-functional acrylate esters... 

The perhydropyrazine (piperazine) heterocycle has been a favorite of the polymer chemist for the preparation of both addition and condensation polymers because of the desirable physical and chemical properties imparted by the ring. Piperazine-functional acrylate esters (140) readily polymerize under free radical conditions (74BRP1361878). Polymers obtained from these monomers, due to the presence of tertiary amino groups, exhibit enhanced dyeabilities and are susceptible to quaternization to form hydrophilic polymers or polyelectrolytes. 

In addition to the equipment properties and selected operating conditions, the process performance depends to a large extent on the state of the active solvent component(s). Commonly nsed solvents include physical solvents like methanol (Rectisol) and the dimethyl ethers of polyethylene glycol (Selexol), chemical solvents like aqneous solutions of carbonates such as K2CO3 and Na2C03, of amino acid salts such as mixtures of potassium hydroxide and alanine or tanrine, and especially of alkanolamines such as mono-ethanolamine (MEA), di-ethanolamine (DEA), (activate) methyl-di-ethanolamine (MDEA), di-isopropanolamine (DIPA), di-glycolamine (DGA), 2-amino-2-methyl-l-propanol (AMP), and piperazine (PZ) (1). 

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