Saturated carbon definition

The SnV(7 mechanism is a logical analogue of the Sn2 reaction at saturated carbon that occurs via backside attack of the nucleophile, but it has long been rejected as a feasible pathway on the basis of steric considerations and of early theoretical calculations on a rather crude model system. However, quite recently definite examples of a reactions have been found, and recent theoretical studies show that the SnVo- as well as the SnVtt mechanism is feasible. If imbalance of bond formation and bond cleavage occurs, the dissociative extreme of... 

The terms saturated and unsaturated refer directly the to the chemistry definition of unsaturation. Unsaturated fats contain carbon-carbon double bonds (units of unsaturation), while saturated fats have only completely saturated carbon chains. Saturated fats (like butter and lard) stack together well in the solid state, so they are generally solid at room temperature. The double bonds in unsaturated fats disrupt this lattice in the solid state, making these types of fats (like olive oil and vegetable oil) liquid at room temperature. 

The definition may be applied to saturated carbon-hydride groups. From this definition the intrinsic state values for methyl, methylene, methine and quaternary carbons are 2.000, 1.500, 1.333 and 1.200, respectively. 

The first structural investigations on cydic tetraynes were carried out in 1957 by Sondheimer [23b]. These studies revealed for 2(3) the presence of a center of symmetry that implies a chair conformation in the soUd state, as is known for cyclohexane and 1,6-cyclodecadiyne. Later, more accurate results on the solid state geometry of 2(3) and 2(4) were obtained [72]. In contrast to 2(3), the larger homologue 2(4) adopts a twisted conformation. Structural data has also been obtained for the even more strained cyclotetraynes 17,19 and 77b (R = TIPS) that are tethered by only two saturated carbon atoms [37, 65]. In Fig. 7.1 a comparison between the X-ray structures of 2(3) and 17 showing the top and a side view is displayed. The most relevant parameters and their definition for 2(3), 2(4) and 17 are given in... 

Although the definition of the two processes is purely arbitrary it is generally assumed that destructive hydrogenation (which is characterized by the cleavage of carbon-to-carbon linkage and is accompanied by hydrogen saturation of... 

It should be kept in mind that, in spite of these major variations in the CO2-carbonic acid system, virtually all surface seawater is supersaturated with respect to calcite and aragonite. However, variations in the composition of surface waters can have a major influence on the depth at which deep seawater becomes undersaturated with respect to these minerals. The CO2 content of the water is the primary factor controlling its initial saturation state. The productivity and temperature of surface seawater also play major roles, in determining the types and amounts of biogenic carbonates that are produced. Later it will be shown that there is a definite relation between the saturation state of deep seawater, the rain rate of biogenic material and the accumulation of calcium carbonate in deep sea sediments. 

Combustion of Solid Carbon.—Owing to their importance as fuel, eaibonaceous materials have for centuries been the subject of scientific consideration. For some time prior to the discovery of oxygen, carbon or charcoal was regarded as composed mainly of the essence of combustibility, and Stahl (c. 1697) considered it to be almost pure phlogiston (see p. 11). On this theory, the fact that only a certain quantity of charcoal could bum m a limited supply of air was readily explained on the assumption that phlogiston could not leave a substance unless it had somewhere to go. The air could only absorb a definite amount, and when once fully phlogistieated behaved like a saturated body and refused to take up any more. 

The most definitive stereochemical studies have concerned configurational changes at the a carbon. Alexander et al. (2, 138) showed that (-I-)540-CpFe(CO)2CH(Me)Ph reacts with neat SOg at —60° or — 10°C, or with SO2 in saturated pentane at 27°C, to give the corresponding iS-sulfinate. The specific rotation of the product, [a]546, varied somewhat with the method of synthesis (—186°, —176°, and —158°, respectively). It was concluded that the insertion is a substantially stereospecific process, but whether it involves retention or inversion could not be determined. 

From this state, ring strain facilitated predissociation to a "biradical-like" transition state [135] or vibrational relaxation (k ) to S may occur. It is also conceivable that transition state [135] could be produced directly from S °. Alternatively, molecules in the S ° state could intersystem cross (kST) to the triplet manifold (T ). For 2-alkylidenecyclobutanones, reactivity is manifested in isomerization about the exocyclic carbon-carbon double bond, while for the saturated cyclobutanone derivatives studied, definitive evidence for solution-phase reactivity is not available. If analogy is again made to the vapor-phase photochemistry of cyclobutanone [21], reactivity could conceivably result in decarbonylated products. Indeed, preliminary evidence has been obtained from sensitization experiments employing m-xylene as triplet sensitizer that decarbonylation of a saturated cyclobutanone is enhanced by selective population of its state (35). ... 

This means that methane is CH4, a saturated, symmetrical compound, in which carbon is tetra-valent, and all of the hydrogens are alike. It should be emphasized again that such a formula, which we call a structural or constitutional formula, does not represent the arrangement of the atoms in space, but is simply a plane representation of the most important facts in regard to methane as shown by definite reactions. The structural formulas for methane and the four chlor methanes are then as follows ... 

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