Intermediate writing

A bndged sulfonmm ion is presumed to be an intermediate Write a stepwise mechanism for this reaction... 

The first step of the u-ketoglntarate dehydrogenase reaction involves decarboxylation of the substrate and leaves a covalent TPP intermediate. Write a reasonable mechanism for this reaction. 

Net Synthesis of a-Ketoglutarate a-Ketoglutarate plays a central role in the biosynthesis of several amino acids. Write a sequence of enzymatic reactions that could result in the net synthesis of a-ketoglutarate from pyruvate. Your proposed sequence must not involve the net consumption of other citric acid cycle intermediates. Write an equation for the overall reaction and identify the source of each reactant. 

The two most important pathways that occur in practice are the AAc2 and the BAc2, both of which proceed via a tetrahedral intermediate. Write down these two pathways, paying particular attention to the nature of the attacking species and the protonation and deprotonation steps. 

Now we will turn our attention to the case of a mesomeric group, Z, which is capable of donating a lone pair of electrons into the ring. As before, there are three possible positions of attack for the incoming electrophile. In addition to the nine canonical structures that were considered for the inductive substituent, there is now an extra canonical structure for both the ortho and para substituted Wheland intermediates. Write down these two extra canonical forms, and suggest what effect they will have on the product distribution. 

A fatty acid with an even number of carbon atoms is metabolized to acetyl-CoA, which can enter the citric acid cycle. A fatty acid with an odd number of carbon atoms is metabolized to acetyl-CoA and one equivalent of propionyl-CoA. Two coenz3me-requiring enzymes are needed to convert propionyl-CoA into succinyl-CoA, a citric acid cycle intermediate. Write the two enz3me-catalyzed reactions and indicate the required coenz3mes. 

The first is a bimolecular or S 2 exchange, the second the formation of the next higher complex and the reverse, and the last is the completion of an Sj l substitution by reaction with a five coordinated intermediate. Writing... 

In the presence of a strong acid, i rr-butyl alcohol acts as a base. The resulting conjugate acid produces water and an intermediate. Write the structure of the intermediate. What type of bond cleavage occurs ... 

Equations (2.10), (2.18) and (2.24) provide the flux relations in situations where each of the three separate mechanisms of momentum transfer dominates. However, there remains the problem of finding the flux relations in "intermediate" situations where all three mechanisms may be of comparable importance. This has been discussed by Mason and Evans [7], who assumed first that the rates of momentum transfer due to mechanisms (i) and (ii) should be combined additively. If we write equation (2.10) in the form... 

No mechanistic aspects of organic chemistry (or, for this reason, any reaction intermediates) were ever mentioned by Zemplen in his lectures or writings, nor did he consider or accept their existence. I never heard him mention the names of Meerwein, Ingold, Robinson, or any other pioneers of the mechanistic electronic theory of organic chemistry. The possible role of organic ions was similarly never mentioned. He was. 

Write a structural formula for the carbocation intermediate formed in the dehydration of each of the alcohols in Problem 5 14 (Section 5 10) Using curved arrows show how each carbocation is deprotonated by water to give a mixture of alkenes... 

Write the structure of the carbinolamine intermediate and the imine product formed in the reaction of each of the following... 

Write structural formulas corresponding to the intermediates formed in the con (jugate addition step and in the aldol addition step ... 

Write a structural formula for the acyl cation intermediate in... 

Write the structure of the tetrahedral intermediate formed in each of the reactions given in Problem 20 7... 

Write an equation showing how you could prepare ethyl phenyl ketone from propanenitrile and a Grignard reagent What is the structure of the imine intermediate ... 

Write equations describing the addition-elimination mechanism for the reaction of hexafluorobenzene with sodium methoxide clearly showing the structure of the rate determining intermediate j... 

By analogy to the intermediates given in steps 1-4 of Figure 26 3 write the sequence of acyl groups that are attached to the acyl carrier pro tein in the conversion of... 

G in the presence of a catalytic amount of a Lewis base such as dimethylether, (GH2)20. In addition to the gas-phase pyrolysis of diborane, can be prepared by a solution-phase process developed at Union Garbide Gorp. Decaborane is a key intermediate in the preparation of many carboranes and metaHa derivatives. As of this writing, this important compound is not manufactured on a large scale in the western world and is in short supply. Prices for decaborane in 1991 were up to 10,000/kg. 

Ghromium(IV) and Ghromium(V) Gompounds. The formal oxidation states Cr(IV) and Cr(V) show some similarities. Both states are apparentiy intermediates in the reduction of Cr(VI) to Cr(III). Neither state exhibits a compound that has been isolated from aqueous media, and Cr(V) has only a transient existence in water (55). The majority of the stable compounds of both oxidation states contain either a halide, an oxide, or a mixture of these two. As of this writing, knowledge of the chemistry is limited. 

In the ease of intermediate topography, they assume that there is a eertain eharaeteristie (for a given surfaee) length, r or, whieh defines the size of small domains eharaeterized by the same value of adsorption energy, and write the pair density distribution as... 

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