Ethylammonium nitrate

Thanks to their special properties and potential advantages, ionic liquids may be interesting solvents for biocatalytic reactions to solve some of the problems discussed above. After initial trials more than 15 years ago, in which ethylammonium nitrate was used in salt/water mixtures [29], results from the use of ionic liquids as pure solvent, as co-solvent, or for biphasic systems have recently been reported. The reaction systems are summarized in Tables 8.3-1 and 8.3-2, below. Table 8.3-1 compiles all biocatalytic systems except lipases, which are shown separately in 8.3-2. Some of the entries are discussed in more detail below. 

Ethylammonium nitrate, CH CH,NH NO , was the first ionic liquid to be discovered. Its melting point of 12°C was reported in 1914 and it has since been used as a nonpolluting solvent for organic reactions and for facilitating the folding of proteins. 

Example 2, using ionic liquid ethylammonium nitrate (EAN) as solvent ... 

The development of ionic liquids dates to 1914. The first research efforts involved the synthesis of ethylammonium nitrate. Hurley and Wier at the Rice Institute in Texas, 1948, developed the first ionic liquids with chloro-aluminate ions as bath solutions for electroplating aluminum. These liquids were studied primarily for their applications as electrolytes in electrochemistry technologies such as electroplating, batteries and alloy preparations. 

Historically, the following four main steps must be mentioned the preparation of ethylammonium nitrate [C2H5NH3][N03] by Paul Walden in 1914 is recognized by many as the first IL. This compound has a melting point of 12°C but owing to its high reactivity has not really found a use [1]. This was the outcome of his studies of conductivity and electrical properties of salt solutions, especially nonaqueous solutions of organic salts. He conducted very systematic studies with different solvents and salts, and his special interest was in ammonium salts. But Walden himself pointed on the work... 

Another subtle case, where specific interactions may obscure the effects of Coulombic criticality, is ethylammonium nitrate (EtNH3N03) +l-octanol (Tcs315K) [85], In contrast to all other known examples, the critical point is located in the salt-rich regime at a critical mole fraction of Xc = 0.77. Electrical conductance data indicate strong ion pairing, presumably caused by a hydrogen bond between the cation and anion which stabilizes the pairs in excess to what is expected from the Coulombic interactions [85]. This warns that, beyond the Coulombic/solvophobic dichotomy widely discussed in the literature, additional mechanisms may affect the phase separation [5]. 

The history of ionic liquids began with the synthesis of ethylammonium nitrate reported in 1914 by Walden [1]. This material is probably the first described in the literature that fulfills the definition of ionic liquids used today. In this context it... 

Figure 2.9 Potential of the fuel cell under load using ethylammonium nitrate as electrolyte. Comparison is made with the behavior of the identical cell with phosphoric acid substituted for the ethylammonium nitrate electrolyte.

Especially to be noted is the high potential of the cell relative to the value obtained when the IL is replaced by 98% H3PO4 with, (0.9 vs. 0.75 V), which is maintained under load when using ethylammonium nitrate as electrolyte. It is evident that with the protic ionic liquid, a much higher exchange current density at the oxygen electrode can be obtained than in other fuel cells. 

In principle, such interactions should also apply to other solvents resembling water, and therefore the more general term solvophobic interactions has been proposed [80, 343]. In fact, analogous water-like behaviour has been observed with self-associated solvents other than water, e.g. ethanol [81], glycerol [82], ethylammonium nitrate [227], and some dipolar non-HBD solvents [228]. 

Ethylammonium nitrate (entry 18 in Table 3-1) was shown in 1914 to have m.p. 12 °C and was hence the first room temperature ionic Hquid [156] this was followed in 1967 by tetra- -hexylammonium benzoate with m.p. —50 °C (entry 26) [169], Ambient-temperature ionic liquids based on l-alkyl-3-methylimidazolium salts (entries 19-24) were first reported by Wilkes et al. in 1982 as tetrachloroaluminates [162a], Replacement of this moisture-sensitive anion by the tetrafluoroborate ion and other anions led, in 1992, to air- and water-stable, room temperature ionic liquids [162b], which have since found increasing application as reaction media for various kinds of organic reactions, mainly owing to the work of Seddon [167, 190] and Hussey [187], Suitably selected... 

Fig. 2 Coexistence curves of the systems tetrabutylammonium picrate + tridecanol and ethylammonium nitrate + octanol. x, is the mole fiaction of the salt.

There is no proton. The cation, NO+, must be counted the acid, and the anion, NOg , the base characteristic of the system. Zinc dissolves in liquid N0O4 evolving nitric oxide and forming [N0+]2[Zn(N03)4] . This compound is an acid in dinitrogen tetroxide and reacts with ethylammonium nitrate, a base in the solvent ... 

Ionic liquids have been known for nearly a century the first to be discovered was ethylammonium nitrate, CH3CH2Nl l3 a melting point of... 

Heimburg, T., Mirzaev, S.Z., and Kaatze, U. Heat capacity behavior in the critical region of the ionic binary mixture ethylammonium nitrate - n-octanol. Phys. Rev. E, 2000, 62, p. 4963-76. 

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