Identifying covalent compounds

Compare and contrast the two covalent compounds identified by the names arsenic(III) oxide and diarsenic trioxide. 

The coupling of the GPC spin column/ESI-MS screening results with NMR (2D HSQC) is a powerful method for confirming that the non-covalent binders identified by the MS experiments truly bind at the predicted active site by observing NMR chemical shift perturbations in the vicinity of the protein active site [1, 15]. In contrast, the absence of chemical shift perturbations or a random distribution of chemical shift changes on the protein surface would imply a lack of an interaction of the compound with the protein or potentially the existence of non-specific binding. The development of the GPC spin column/MS/NMR assay... 

The ability to name compounds and determine the chemical formula for a compound comes from the ability to distinguish between ionic and covalent compounds. The name of a compound depends heavily on the type of bond present between the atoms. Besides being able to identify certain types of bonds, when learning to name compounds it is best to remember the rules that apply to the type of bond in question. The rules for naming four common kinds of compounds are outlined below. 

Adds and Bases. Generally, acids react according to the rules for replacement and double replacement reactions. They are so important however, that a special nomenclature has developed for acids and their reactions. Acids were introduced in Chapter 5. They may be identified by their formulas, which have the H representing hydrogen written first, and by their names, which contain the word acid. An acid will react with a base to form a salt and a water. The process is called neutralization. The driving force for such reactions is the formation of water, a covalent compound. For example. 

Now that you know that two major types of compounds exist, you may wonder where else you come into contact with these compounds on a day-to-day basis. In Chapter 5, you ll look at more examples of ionic and covalent compounds, including compounds more complex than the simple ones used as examples in this chapter. You ll also learn the important practical skill of naming and writing the formulas of compounds, as well as how to identify a few special categories of compounds such as acids, bases, and organic compounds. 

Given a formula or name for a compound, identify whether it represents a binary covalent compound. 

Most of the compounds identified in the degraded non-extractable residues represent the unaltered bound substances and reflect the incorporated proportion of organic pollutants introduced into the aquatic environment by anthropogenic emissions. The major portion of these substances was not associated by covalent linkages but by weaker interactions. 

For ionic compounds, this formula is enough to fully identify the compound, but it s not enough to identify covalent compounds. Look at the Lewis formulas presented in Figure 7-5. Both compounds have the molecular formula of C2H6O. 

To identify the exact covalent compound, you need its structural formula. 

Mercuric salts (HgXg) are Lewis acids that react readily with alkenes, and experiments show that the reaction proceeds by formation of a carboca-tion intermediate. When mercuric acetate—HgCOAcla see the structure and Chapter 20, Section 20.5—reacts with 3-methyl-l-hexene in a THF-water mixture, the isolated product is a mercuric compound identified as 71 (with a C-Hg bond) and it is formed by reaction of water with a carbocation intermediate. The initial acid-base reaction is the donation of the 7i-electrons to form a new C-Hg covalent bond, leaving behind a carbocation at the other carbon of the C=C unit. 

PRACTICE the skill 1.15 For each of the following compounds, identify any polar covalent bonds by drawing... 

A series of compounds identified during our HTS featured small dipeptides with the C-terminus replaced by a heterocyclic ketone moiety as exemplified by compound 6. We were pleased to see the high activity of 6 (59 nM) and assumed that the activated ketone residue might act as a covalent-reversible inhibitor of CatA. 

Compounds that have the same moleculcir formula but different structures eire called isomers of each other. To identify the exact covalent compound, you need its structural formula. 

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