Why cations are lewis acids

Heterocyclic monomers that are cationically polymerized are Synthesis [ ] Initiation [ ] Initiation is the first step in cationic polymerization. During initiation, a Classical protic acids [ ] Strong −) produced must be weakly nucleophilic so as to prevent early termination due to combination with the protonated alkene. Carbenium ion salts [ ] Stable carbenium ions are used to initiate chain growth of only the most reactive alkenes and are known to give well defined structures. These initiators are most often used in kinetic studies due to the ease of measuring the disappearance of the carbenium ion absorbance. Common carbenium ions are Effect of temperature [ ] The temperature of the reaction has an effect on the rate of propagation. The overall activation energy for the polymerization ( E , meaning the overall Chain length is also affected by temperature. Low reaction temperatures, in the range of 170–190 K, are preferred for producing longer chains. Effect of solvent and counterion [ ] The solvent and the counterion (the gegen ion) have a significant effect on the rate of propagation. The counterion and the carbenium ion can have different associations according to Range of associations between the R + ) The association is strongest as a covalent bond and weakest when the pair exists as free ions. The size of the counterion is also a factor. A smaller counterion, with a higher charge density, will have stronger electrostatic interactions with the carbenium ion than w...

• Afrikaans • العربية • বাংলা • Bosanski • Català • Čeština • Deutsch • Eesti • Ελληνικά • Español • Euskara • فارسی • Français • हिन्दी • Hrvatski • Bahasa Indonesia • Italiano • Latviešu • മലയാളം • 日本語 • Norsk bokmål • Polski • Português • Slovenščina • Српски / srpski • Srpskohrvatski / српскохрватски • தமிழ் • Türkçe • Tiếng Việt • 中文 • v • t • e A Lewis acid (named for the American physical chemist Lewis base, then, is any species that has a filled orbital containing an electron pair which is not involved in 3 is a Lewis base, because it can donate its 3B) is a Lewis acid as it is capable of accepting a lone pair. In a Lewis adduct, the Lewis acid and base share an electron pair furnished by the Lewis base, forming a dative bond. 3 and Me 3B, a lone pair from NH 3 will form a dative bond with the empty orbital of Me 3B to form an adduct NH 3•BMe 3. The terminology refers to the contributions of The terms nucleophilicity and electrophilicity, emphasize the Depicting adducts [ ] In many cases, the interaction between the Lewis base and Lewis acid in a complex is indicated by an arrow indicating the Lewis base donating electrons toward the Lewis acid using the notation of a Me 3B← NH 3. Some sources indicate the Lewis base with a pair of dots (the explicit electrons being donated), which allows consistent representation of the transition from the base itself to the complex with the acid: Me 3B + :NH 3 → Me 3B:NH 3 A center dot may also be used to represent a Lewis adduct...

Coordination Complexes Coordination compounds, such as the FeCl 4 - ion and CrCl 3 6 NH 3, are called such because they contain ions or molecules linked, or coordinated, to a transition metal. They are also known as complex ions or coordination complexes because they are Lewis acid-base complexes. The ions or molecules that bind to transition-metal ions to form these complexes are called ligands (from Latin, "to tie or bind"). The number of ligands bound to the transition metal ion is called the coordination number. Although coordination complexes are particularly important in the chemistry of the transition metals, some main group elements also form complexes. Aluminum, tin, and lead, for example, form complexes such as the AlF 6 3-, SnCl 4 2- and PbI 4 2- ions. Werner's Theory of Coordination Complexes Alfred Werner developed a model of coordination complexs which explains the following observations. • At least three different cobalt(III) complexes can be isolated when CoCl 2 is dissolved in aqueous ammonia and then oxidized by air to the +3 oxidation state. A fourth complex can be made by slightly different techniques. These complexes have different colors and different empirical formulas. CoCl 3 6 NH 3 orange-yellow CoCl 3 5 NH 3 H 2O red CoCl 3 5 NH 3 purple CoCl 3 4 NH 3 green • The reactivity of the ammonia in these complexes has been drastically reduced. By itself, ammonia reacts rapidly with hydrochloric acid to form ammonium chloride. NH 3( aq) + HCl( aq) NH 4 +(...

Table of Contents • • • • • • • • • Are metal cations Lewis acids? Metal cations are potential Lewis acids. Why are metal cations good Lewis acids? A Lewis acid is an electron pair acceptor; because metal ions have one or more empty orbitals, they act as Lewis acids when coordinating ligands. Examples of metals that can act as Lewis acids include Na+, Mg2+, and Ce3+. Are cations usually Lewis acids? Cations are electron-deficient species and can accept an electron pair. Hence, cations are Lewis acids. Are highly charged metal cations Lewis acids? Instead, a metal ion can act as a Lewis acid and interact with water, a Lewis base, by coordinating to a lone pair of electrons on the oxygen atom to form a hydrated metal ion. A water molecule coordinated to a metal ion is more acidic than a free water molecule for two reasons. Why cations are Lewis acid and anions are Lewis base? 1 Answer. Since cations are deficient of electrons they accept a pair of electrons, hence they are Lewis acids. Are cations acids or bases? Again, the cations (K+ and Na+) have essentially no acidic character, but the anions (CN− and CH3CO−2) are weak bases that can react with water because they are the conjugate bases of the weak acids HCN and acetic acid, respectively. Why cations are Lewis acids and anions are Lewis bases? Are smaller cations more acidic? The Lewis Acidity of Cations. The more positive the cation charge, the greater the tendency of the cation to accept electron pairs from Lewis bases...

Cations as Lewis Acids Molecules as Further investigations are under way concerning the properties of the cations as The electrophile 4 adds to the When a complex ion is formed from a Small, highly To remove an ion, we can use the fact that many Hydroxy-L-prolin is converted into a 2-methoxypyrrolidine. This can be used as a valuable The This Reactions of P-halogen-NHPs I 8.5 Judging from these findings, the mechanism of In the course of our investigations to develop new When a In this chapter, we have discussed the application of See other pages where Cations as Lewis Acids is mentioned: See also in sourсe #XX -- [ SEARCH © 2019

\( \newcommand\) • • • • • Learning Objectives • To recognize salts that will produce acidic, basic, or neutral solutions in water • To understand the Lewis acidity of small, highly-charged metal ions in water A neutralization reaction can be defined as the reaction of an acid and a base to produce a salt and water. That is, another cation, such as \(Na^+\), replaces the proton on the acid. An example is the reaction of \(CH_3CO_2H\), a weak acid, with \(NaOH\), a strong base: \[\underset\), have different sizes and charges, but similar charge-to-radius ratios. As a result, these pairs of metal ions have similar effects on the acidity of coordinated water molecules, and they often exhibit other significant similarities in chemistry as well. Solutions of small, highly charged metal ions in water are acidic. Reactions such as those discussed in this section, in which a salt reacts with water to give an acidic or basic solution, are often called hydrolysis reactions. Using a separate name for this type of reaction is unfortunate because it suggests that they are somehow different. In fact, hydrolysis reactions are just acid–base reactions in which the acid is a cation or the base is an anion; they obey the same principles and rules as all other acid–base reactions. A hydrolysis reaction is an acid–base reaction. Example \(\PageIndex\) ion will react with water as shown in Figure 16.6 to give a slightly basic solution. Summary A salt can dissolve in water to produce a neutral,...

The strength of Lewis acids relative to your Lewis base has been commented on. A fuller answer to your question needs to include the Lewis acid you are considering. The original Bronsted-Lowry theory of comparing acidity and basicity, or acids and bases, involved $\ce$ as an alkali. Stretching the word "base" by adding "Lewis" in front of it needs more, like adding the reference acid, to make the comment clear rather than confusing. Thanks for contributing an answer to Chemistry Stack Exchange! • Please be sure to answer the question. Provide details and share your research! But avoid … • Asking for help, clarification, or responding to other answers. • Making statements based on opinion; back them up with references or personal experience. Use MathJax to format equations. To learn more, see our