Reactivity electronegativity

The chemical literature bristles with failed attempts to find a quantum-mechanical model that accounts for all aspects of chemistry, including chemical bonding, molecular structure, molecular rearrangement, stereochemistry, photochemistry, chirality, reactivity, electronegativity, the valence state and too many more to mention. A small group of enthusiasts still believe that it s all a question of computing power, but that hope is also fading fast. 

Perhaps the most interesting thing about the Periodic Table of Elements is how much information is hidden in it. To the untrained eye, the periodic table appears to only show the elemental symbols, elemental names, atomic numbers, and atomic masses. However, someone who knows a bit more chemistry can squeeze much more information out of the same table. You will learn to use the periodic table to check your electron configurations, orbital notations, and Lewis dot notations. You will also learn to use the periodic table to check many relative properties of the elements, such as reactivity, electronegativity, and metallic character. All of this information is there, if you know how to use the table correctly. It is certainly in your best interest to learn as much about the periodic table as possible, because you are allowed to make use of it on many exams and quizzes. If you are able to extract all kinds of information from it, it becomes an incredibly useful cheat sheet, except that you re allowed to use it ... 

The specific measure of chemical reactivity, electronegativity (x), which lacks a definite quantum operator but retains an observable character through... 

Fluorine is the most electronegative and reactive of all elements. It is a pale yellow, corrosive gas, which reacts with most organic and inorganic substances. Finely divided metals, glass, ceramics, carbon, and even water burn in fluorine with a bright flame. 

The opening paragraph of this chapter emphasized that the connection between structure and properties is what chemistry is all about We have just seen one such con nection From the Lewis structure of a molecule we can use electronegativity to tell us about the polarity of bonds and combine that with VSEPR to predict whether the mol ecule has a dipole moment In the next several sections we 11 see a connection between structure and chemical reactivity as we review acids and bases... 

One reason for the low reactivity of pyridine is that its nitrogen atom because it IS more electronegative than a CH in benzene causes the rr electrons to be held more tightly and raises the activation energy for attack by an electrophile Another is that the nitrogen of pyridine is protonated in sulfuric acid and the resulting pyndinium ion is even more deactivated than pyndine itself... 

The reactivity of the individual O—P insecticides is determined by the magnitude of the electrophilic character of the phosphoms atom, the strength of the bond P—X, and the steric effects of the substituents. The electrophilic nature of the central P atom is determined by the relative positions of the shared electron pairs, between atoms bonded to phosphoms, and is a function of the relative electronegativities of the two atoms in each bond (P, 2.1 O, 3.5 S, 2.5 N, 3.0 and C, 2.5). Therefore, it is clear that in phosphate esters (P=0) the phosphoms is much more electrophilic and these are more reactive than phosphorothioate esters (P=S). The latter generally are so stable as to be relatively unreactive with AChE. They owe their biological activity to m vivo oxidation by a microsomal oxidase, a reaction that takes place in insect gut and fat body tissues and in the mammalian Hver. A typical example is the oxidation of parathion (61) to paraoxon [311-45-5] (110). 

The Q and e values of VP are 0.088 and —1.62, respectively (125). This indicates resonance interaction of the double bond of the vinyl group with the electrons of the lactam nitrogen, whence the electronegative nature. With high e+ monomers such as maleic anhydride, VP forms alternating copolymers, much as expected (126). With other monomers between these Q and e extremes a wide variety of possibiHties exist. Table 14 Hsts reactivity ratios for important comonomers. 

Fluorine is a small atom with a large ego. Fluorine has a high electronegativity so it makes it very reactive, bonding with a great number of atoms. 

The concepts of electronegativity, hardness, and polarizability are all interrelated. For the kind of qualitative applications we will make in discussing reactivity, the concept that initial interactions between reacting molecules can be dominated by either partial electron transfer by bond formation (soft reactants) or by electrostatic interaction (hard reactants) is a useftxl generalization. 

The reactivity of mercury salts is a fimction of both the solvent and the counterion in the mercury salt. Mercuric chloride, for example, is unreactive, and mercuric acetate is usually used. When higher reactivity is required, salts of electronegatively substituted carboxylic acids such as mercuric trifiuoroacetate can be used. Mercuric nitrate and mercuric perchlorate are also highly reactive. Soft anions reduce the reactivity of the Hg " son by coordination, which reduces the electrophilicity of the cation. The harder oxygen anions leave the mercuric ion in a more reactive state. Organomercury compounds have a number of valuable synthetic applications, and these will be discussed in Chapter 8 of Part B. 

Molecular iodine is not a very powerful halogenating agent. Only very reactive aromatics such as anilines or phenolate anions are reactive toward iodine. Iodine monochloride can be used as an iodinating agent. The greater electronegativity of the... 

The ease with which an atom gains or loses electrons is termed die electronegativity of die element. Tabulation of die elements in order of ease hy which diey lose electrons is called die electrochemical series and is shown in Table 6.10. Chapter 4 explains die importance of diis to die formation and control of coiTosion, and Chapter 6 discusses die relevance to predicting reactivity of metals towards water and their potential to become pyrophoric. 

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