Synthesis empirical rules

Kolbe hydrocarbon synthesis orgchem The production of an alkane by the electrolysis of a water-soluble salt of a carboxylic acid. kol-bo. hT-dro kar-bon, sin-th3-s3s Kolbe-Schmitt synthesis org chem The reaction of carbon dioxide with sodium phenoxide at 125°C to give salicyclic acid. kol-bo shmit, sin-th3-s3s Konowaioff ruie phys chem An empirical rule which states that in the vapor over a liquid mixture there is a higher proportion of that component which, when added to the liquid, raises its vapor pressure, than of other components., k6-n9 va-lof, rul ... 

Essentially all publications published in the period since CHEC-II(1996) dealing with the synthesis, structural characterization, or properties of pyran-containing molecules are replete with nuclear magnetic resonance (NMR) data. While the empirical rules summarized in CHEC(1984) and CHEC-II(1996) remain of value for the... 

Although the synthesis rules are routinely formulated in terms of hybrid orbitals, they are in fact purely empirical, and not entirely logical. On the one hand an electrophile, H+ is shown (2) to react with the pair of 7r-electrons of a C - C double bond to generate an intermediate carbocation. In the inverse process (3) a base (B ) is shown to attack through a C-H single bond without specifying the orbital that transfers the electron pair from C-H (double bond ) to C-C. This is an unnecessary complication as the empirical rules work well without the orbital baggage. 

The substrate of the present reaction is not limited to allylic alcohols. Alke-nyldimethylsilanols, which are structurally similar to allylic alcohols, are amenable to epoxidation. For example, epoxidation of silanol4 using (-i-)-DIPT as the chiral source provides the (2S,3S)-epoxydisiloxane 5 in 90% ee, the configuration of which is consistent with the empirical rule (Scheme 4) [29]. Protodesi-lylation of 5 with fluoride ion provides the terminal epoxide 6. This procedure is a useful method for the synthesis of simple terminal epoxides. 

In Section 2.6 we discussed the nature of cause and effect, and in Section 7.2 we noted that empirical rules are obtained inductively from observations and experiences regarding real structures from three broad categories of situation, success, failure and the near-miss or narrowly avoided failure. Information about successful projects enables us to identify sufficient conditions for success failures tell us the necessary conditions for success. What we would like, of course, are the conditions which are necessary and sufficient but we will never be in that position, for we will never know that there are no unknown phenomena which could occur. Our technical knowledge enables us usually to describe, at least approximately, the technical causal chain in any success or failure. The variancy (Section 2.6) involves all the factors not accounted for in our analytical models, whether theoretical or physical, and it is from this that we learn our lessons for the future. In effect the engineer s judgement based upon his experience is the result of his synthesis of these factors in a teleological explanation. 

As to the space requirements, not only cations with the optimum radius were incorporated. Some bulky cations such as Ga ", Ti Sb " etc were incorporated as well (14-16). Therefore, the rules set up for incorporation must be considered as empirical rules that do not ensure (nor exclude) the incorporation of a given element and rather as general guidelines, each element must be considered as a special case. Consequently, the primary task of the synthesis chemist is to jBnd reliable criteria of incorporation. 

A novel suggestion, with an illustration, has come from Kametani. He proposes that chemists should design their syntheses on the basis of the mass spectral fragmentation of the target molecule in question, and he provides examples from amongst the natural quinazolones. Finally, Baldwin has provided some empirical rules which allow the chemist to predict the success or otherwise of ring-closure reactions in synthesis, and has extended the rules in consecutive papers on his Approach Vector Analysis, to provide a stereochemical approach to reactivity. 

Foulkes et al. (1988) have approached the synthesis of operating procedures from a more empirical angle. They have extended the work of Rivas and Rudd (1974) for the synthesis of complex pump and valve sequencing operations, relying on the use of logical propositions (implemented as rule-based expert systems), which capture the various types of constraints imposed on the states of a processing system. 

Comparison of the potassium content of the cetineite crystals to the composition of the synthesis mixture shows a preferred incorporation of potassium into the structure. Although this compound with 50 atoms per unit cell is a highly complex structure, it seems to follow the empirical Vegard s rule similar to homogeneous mixed crystals and for intermetallic phases of the Laves type as well as to microporous tin(IV)thioselenides of type SnSi.xSex.i.[13]... 

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