What is an

A protein can be identified as an E2 enzyme according to several different criteria. Functionally, the E2 occupies an intermediate position in the conjugation cascade - 

Structural biology provides a final way to define an E2 enzyme. As expected from the strong sequence conservation, the E2 core domain adopts a conserved fold. At the time this article was being prepared, twelve different E2 structures had been deposited in the Protein Data Bank. The average root-mean-square deviation of 

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What is an unsamrated organic compound Give some examples. 

There is no mention that a prior hazard assessment will be acceptable. It is only common sense that OSHA would not expect employers with a previously documented hazard assessment program that meets the new requirements to perform another assessment. Yet there is no way of knowing if this will be acceptable. Employers should use good judgment on what is an effective hazard assessment. Bear in mind, hazard assessment should incorporate any applicable American National Standards... 

What is an amino acid sequence of the octapeptide Four sequences are possible, but only one suits the authors. Why ... 

What is an engineering standard Webster s New International Dictionary contains the following definition Standard That which is established by authority, custom, or general consent, as a model or example, criteria, text. In general, a definitive level, degree, material, character, quality, or the like, viewed as that which is proper and adequate for a given purpose. 

The product i n this case is a cis-disubstituted alkene, so the fi rst question is, " What is an immediate precursor of a cis-disubstituted alkene " We know that an alkene can be prepared from an alkyne by reduction and that the right choice of experimental conditions will allow us to prepare either a trans-disubstituted alkene (using lithium in liquid ammonia) ora cis-disubstituted alkene (using catalytic hydrogenation over the Lindlar catalyst). Thus, reduction of 2-hexyne by catalytic hydrogenation using the Lindlar catalyst should yield cis-2-hexene. 

Next ask, "What is an immediate precursor of 2-hexyne " We ve seen that an internal alkyne can be prepared by alkylation of a terminal alkyne anion. In the present... 

Strategy Identify the functional group in the product (an alkyl bromide) and work the problem retrosynthetically. "What is an immediate precursor of an alkyl bromide " Perhaps an alkene plus HBr. Of the two possibilities, addition of HBr to 1-pentene looks like a better choice than addition to 2-peritene because the latter reaction would give a mixture of isomers. 

What is an immediate precursor of an alkene " Perhaps an alkyne, which could be reduced. 

What is an immediate precursor of a terminal alkyne " Perhaps sodium acetylide and an alkyl halide. 

Strategy What is an immediate precursor of a primary alcohol " Perhaps a terminal alkene, which could be hydrated with non-Markovnikov regiochemistiy by reaction with borane Followed by oxidation with H2O2-... 

During our previous discussion of strategies for working synthesis problems in Section 8.9, we said that ids usually best to work a problem backward, or retrosyntheticnlly. Look at the target molecule and ask yourself, "What is an immediate precursor of this compound " Choose a likely answer and continue working backward, one step at a time, until you arrive at a simple starting material. Let s try some examples. 

Next ask yourself, "What is an immediate precursor of p-bromotoluene " Perhaps toluene is an immediate precursor because the methyl group would direct bromination to the ortho and para positions. Alternatively, bromobenzene might be an immediate precursor because we could carry out a Friedel-Cralts methylation and obtain a mixture of ortho and para products. Both answers are satisfactory, although both would also lead unavoidably to a product mixture that would have to be separated. 

What is an immediate precursor of toluene " Benzene, which could be methylated in a Friedel-Crafts reaction. Alternatively, "What is an immediate precursor of bromobenzene " Benzene, which could be brominated. 

Solution "What is an immediate precursor of the target " The final step will involve introduction of one of three groups—chlorine, propyl, or sulfonic acid—so we have to consider three possibilities. Of the three, the chlorination of o-propylbenzene-sulfonic acid can t be used because the reaction would occur at the wrong position. Similarly, a Friedel-Crafts reaction can t be used as the final step because this reaction doesn t work on sulfonic acid-substituted (strongly deactivated) benzenes. Thus, the immediate precursor of the desired product is probably m-chloropropyl-benzene, which can be sulfonated to give a mixture of product isomers that must then be separated. 

What is an immediate precursor of j i-chloropropylbenzene " Because the two substituents have a meta relationship, the first substituent placed on the ring must be a meta director so that the second substitution will take place at the proper position. Furthermore, because primary alkyl groups such as propyl can t be introduced directly by Friedel-Crafts alkylation, the precursor of... 

What is an immediate precursor of m-chloropropiophenoire " Propiophenone, wliich could be chlorinated in the meta position. 

Suppose that 10.0 g of an organic compound used as a component of mothballs is dissolved in 80.0 g of benzene. The freezing point of the solution is 1.20°C. (a) What is an approximate molar mass of the organic compound (b) An elemental analysis of that substance indicated that the empirical formula is C3H2C1. What is its molecular formula (c) Using the atomic molar masses from the periodic table, calculate a more accurate molar mass of the compound. 

For what is an apparently straightforward problem, wavefront sensing has produced a large number of apparently quite different solutions (for example the Shack-Hartmann (Lane and Tallon, 1992), curvature (Roddier, 1988) and pyramid (Ragazzoni, 1996) sensors). Underlying this diversity is the problem... 

Explain the concepts of atom efficiency and environmental friendliness. What is an E-factor Which processes usually have the highest E-factors Explain what catalysis means on the different length scales indicated in Eig. 1.8. 

The Alchemist is about a stranger that came to the Kingdom and brought a little silver bottle whose contents changed the women in the land. What is an Alchemist You ll find out at the end of the book (Does not contain any magic or things offensive to believers.)... 

Can an open-loop be still a loop You may wonder what is an open-loop Often, we loosely refer elements or properties of part of a system as open-loop, as opposed to a complete closed-loop system. You ll see more of this language in Chapter 7. 

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