Polar reaction curved arrows

Table 6.1 summarizes the many kinds of arrows used in describing organic reactions. Curved arrows are especially important because they explicitly show what electrons are involved in a reaction, how these electrons move in forming and breaking bonds, and if a reaction proceeds via a radical or polar pathway. 

Most carboxylic acids dissolve in aqueous solutions of sodinm bicarbonate (NaHCOa) because, as carboxylate salts, they are more polar. Write curved arrows showing the reaction... 

As we saw in Section 2.11, chemists indicate the movement of an electron pair during a polar reaction by using a curved, full-headed arrow. A curved arrow shows where electrons move when reactant bonds are broken and product bonds are formed. It means that an election pair moves from the atom... 

Using Curved Arrows in Polar Reaction Mechanisms 149... 

Add curved arrows to the following polar reaction to show the flow of electrons ... 

Problem 5.9 Predict the products of the following polar reaction, a step in the citric acid cycle for food metabolism, by interpreting the flow of elections indicated by Uie curved arrows ... 

A full description of how a reaction occurs is called its mechanism. There are two general kinds of mechanisms by which reactions take place radical mechanisms and polar mechanisms. Polar reactions, the more common type, occur because of an attractive interaction between a nucleophilic (electron-rich) site in one molecule and an electrophilic (electron-poor) site in another molecule. A bond is formed in a polar reaction when the nucleophile donates an electron pair to the electrophile. This movement of electrons is indicated by a curved arrow showing the direction of electron travel from the nucleophile to... 

Historically, ethylene potymerization was carried out at high pressure (1000-3000 atm) and high temperature (100-250 °C) in the presence of a catalyst such as benzoyl peroxide, although other catalysts and reaction conditions are now more often used. The key step is the addition of a radical to the ethylene double bond, a reaction similar in many respects to what takes place in the addition of an electrophile. In writing the mechanism, recall that a curved half-arrow, or "fishhook" A, is used to show the movement of a single electron, as opposed to the full curved arrow used to show the movement of an electron pair in a polar reaction. 

Rules for using curved arrows in polar reaction mechanisms (Section 5.6). 

Using Curved Arrows In Polar Reaction Mechanisms... 

Probtem S.7 Frediir th producw of the followin(f polar reaction b>- interpreting Uie How of electrons a indicated by tbe curved arrow) -... 

Look closely at the acid-base reactions in Figure 2.5, and note how they are shown. In the first reaction, the Lewis base water uses an electron pair to abstract H from the polar HCl molecule. In the remaining two reactions, a Lewis base donates an electron pair to a vacant valence orbital of a boron or aluminum atom. In all three reactions, the direction of electron-pair flow from the electron-rich Lewis base to the electron-poor Lewis acid is shown using curved arrows, just as the direction of electron flow in going from one resonance structure to another was shown using curved arrows in Section 2.5. A curved arrow always means that a pair of electrons moves from the atom at the tail of the arrow to the atom at the head of the arrow. 

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