Self spontaneous

An intense purple crystalline solid m.p. 219-220 C. One of the few monomeric cyclo-pentadienone derivatives, most of which spontaneously undergo self Diels-Alder type dimerization. Used as a diene in many studies of various aspects of the Diels-Alder reaction. ... 

Self-assembled monolayers (SAMs) are molecular layers tliat fonn spontaneously upon adsorjDtion by immersing a substrate into a dilute solution of tire surface-active material in an organic solvent [115]. This is probably tire most comprehensive definition and includes compounds tliat adsorb spontaneously but are neither specifically bonded to tire substrate nor have intennolecular interactions which force tire molecules to organize tliemselves in tire sense tliat a defined orientation is adopted. Some polymers, for example, belong to tliis class. They might be attached to tire substrate via weak van der Waals interactions only. 

This mode of molecular recognition, on principle, is defined as the recognition of like from unlike or self from unself-molecules, embodied in the spontaneous selection and preferential assembly of like components in a mixture (9). 

A particular point of interest included in these hehcal complexes concerns the chirality. The heUcates obtained from the achiral strands are a racemic mixture of left- and right-handed double heUces (Fig. 34) (202). This special mode of recognition where homochiral supramolecular entities, as a consequence of homochiral self-recognition, result from racemic components is known as optical self-resolution (203). It appears in certain cases from racemic solutions or melts (spontaneous resolution) and is often quoted as one of the possible sources of optical resolution in the biological world. On the other hand, the more commonly found process of heterochiral self-recognition gives rise to a racemic supramolecular assembly of enantio pairs (204). 

A second class of monolayers based on van der Waal s interactions within the monolayer and chemisorption (in contrast with physisorption in the case of LB films) on a soHd substrate are self-assembled monolayers (SAMs). SAMs are well-ordered layers, one molecule thick, that form spontaneously by the reaction of molecules, typically substituted-alkyl chains, with the surface of soHd materials (193—195). A wide variety of SAM-based supramolecular stmctures have been generated and used as functional components of materials systems in a wide range of technological appHcations ranging from nanoHthography (196,197) to chemical sensing (198—201). 

Unfortunately, because self-condensation of silanols on the same silicone can occur almost spontaneously, the reaction of disdanol or trisilanol compounds with telechelic sdanol polymers to form a three-dimensional network is not feasible. Instead, the telechelic polymers react with cross-linkers containing reactive groups such as alkoxysdanes, acyloxysdanes, silicon hydrides, or methylethyloximesilanes, as in the reactions in equations 18—21 (155). 

Formation of Hposomal vesicles under controlled conditions of emulsification of Hpids with phosphoHpids has achieved prominence in the development of dmgs and cosmetics (42). Such vesicles are formed not only by phosphoHpids but also by certain nonionic emulsifying agents. Formation is further enhanced by use of specialized agitation equipment known as microfluidizers. The almost spontaneous formation of Hposomal vesicles arises from the self-assembly concepts of surfactant molecules (43). Vesicles of this type are unusual sustained-release disperse systems that have been widely promoted in the dmg and cosmetic industries. 

Like many other combustible Hquids, self-heating of ethyleneamines may occur by slow oxidation in absorbent or high-surface-area media, eg, dumped filter cake, thermal insulation, spill absorbents, and metal wine mesh (such as that used in vapor mist eliminators). In some cases, this may lead to spontaneous combustion either smoldering or a flame may be observed. These media should be washed with water to remove the ethyleneamines, or thoroughly wet prior to disposal in accordance with local and Eederal regulations. 

A (macro)emulsion is formed when two immiscible Hquids, usually water and a hydrophobic organic solvent, an oil, are mechanically agitated (5) so that one Hquid forms droplets in the other one. A microemulsion, on the other hand, forms spontaneously because of the self-association of added amphiphilic molecules. During the emulsification agitation both Hquids form droplets, and with no stabilization, two emulsion layers are formed, one with oil droplets in water (o /w) and one of water in oil (w/o). However, if not stabilized the droplets separate into two phases when the agitation ceases. If an emulsifier (a stabilizing compound) is added to the two immiscible Hquids, one of them becomes continuous and the other one remains in droplet form. 

The principal difficulty associated with this type of synthesis is in the availability of a-aminoacyl compounds, e.g. a-aminoaldehydes, a-aminoketones, etc., and most type B syntheses rely on the generation of these compounds in situ, where the self-condensation occurs spontaneously. A large number of research groups have addressed themselves to this problem and a variety of routes are now available. 

Certain materials which are generally considered to be stable at ordinary temperatures can inflame even in tlie absence of normal ignition sources. Such spontaneous combustion results from exotliermic autoxidation when the heat liberated exceeds that dissipated by the system. Materials prone to self-heating are listed in Table 6.7. In most cases, such fires involve relatively large, enclosed or thermally-insulated masses, and spontaneous combustion usually occurs after prolonged storage. 

The antoignition temperatnre of a gas or vapor is the minimnm temperatnre at which it will ignite in air withont any external sonrce of ignition (e.g., a flame, spark, hot snrface etc.). It is often also called the spontane-ons-ignition or self-ignition temperatnre. The measnrement of AIT depends on many factors, snch as molecnlar stmctnre of the gas/vapor. 

Insulin is composed of two peptide chains covalently linked by disulfide bonds (Figures 5.17 and 6.35). This monomer of insulin is the active form that binds to receptors in target cells. However, in solution, insulin spontaneously forms dimers, which themselves aggregate to form hexamers. The surface of the insulin molecule that self-associates to form hexamers is also the surface that binds to insulin receptors in target cells. Thus, hexamers of insulin are inactive. 

Selbst-. self-, automatic, spontaneous, auto-, selbstabdichtend, a. self-sealing. 

Selbstachtung,/. self-respect, self-esteem, selbstandlg, a. Independent, self-dependent spontaneous. 

Selbstdlffusion, /. self-diffusion, autodififuslon. selbstemulgierend, a. self-emulslfylng. selbstentzund-bar, -lich, a. spontaneously (in)-flammable. 

Selbst-lbschung, /. (of lime) spontaneous slaking. -I dtung,/. autogenic soldering, -oxyda-tion,/. autoxidation, self-oxidation. 

---