Arrow Notations, Electrophile and Nucleophiles

 

Before you explore the specific mechanism, there are some important terms you need to understand which are shown in the links provided below:

1. (a) Follow this link for helpful advice on how to draw curly arrows when describing organic reaction mechanisms. Curly Arrows
2. (a) Definitions of electrophile and nucleophile.

Electrophile:   An electron deficient atom, ion or molecule that has an

affinity for an electron pair, and will bond to a base or nucleophile. 

It is something which is attracted to electron-rich regions in other molecules

or ions. Because it is attracted to a negative region, an electrophile must

be something which carries either a full positive charge, or has a slight

positive charge on it somewhere. Eg. of electrophiles:  cations such as

H+ and NO+, HCl, alkyl halides(CH3Cl),acyl halides, and carbonyl compounds,

Cl2 and Br2, and some lewis acids such as BH3 , AlCland carbocations

(or called carbonium ions).

Nucleophile:   An atom, ion or molecule that has an electron pair that may

be donated in bonding to an electrophile (or Lewis acid).

It is a species (an ion or a molecule) which is strongly attracted to a region

of positive charge in something else. Nucleophiles are either fully negative

ions, or else have a strongly delta negative charge somewhere on a molecule.      

Common nucleophiles are hydroxide ions, cyanide ions, water, ammonia

and carbanions.

The importance of electrophile / nucleophile terminology comes from the fact that many organic reactions involve at some stage the bonding of a nucleophile to an electrophile, a process that generally leads to a stable intermediate or product.

  (b) Electrophile and Nucleophile (The video below gives an interesting explanation of the two terms. )

Organic Chemistry  Lewis Acids.flv Organic Chemistry Lewis Acids.flv
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Type : flv
 
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