Simply Mechanisms 7f Nucleophilic Addition Elimination Ethanoic Anhydride amp Ethanol

>> YOUR LINK HERE: ___ http://youtube.com/watch?v=HURrpExT_8g

http://franklychemistry.co.uk/simply_... • This video looks at the mechanism for nucleophilic addition elimination. These are also called condensation reactions - where two organic molecules join with a small molecule being shed in the process. In this case I look at the reaction of ethanoic anhydride (an acid anhydride) with ethanol. Ethanol is a better nucleophile than water. Alkyl groups are electron-donating. This means the O atom in ethanol is more prepared to share its lone pair, making it a better nucleophile. The carbons of the 2 COO functional groups of an ethanoic anhydride have two small positive charges assigned to them their carbon atoms are bonded to 2 more electronegative atoms (O in both cases). This means that nucleophiles will be attracted strongly. Addition takes place in the first step as the ethanoic anhydride and ethanol molecules join together to form a single unstable intermediate. The second step involves the elimination of both a CH3COO- ion and a hydrogen ion. These form a molecule of ethanoic acid. The remainder of the intermediate is a molecule of the ester ethyl ethanoate. Other nucleophiles that react with ethanoic anhydride, in order of increasing vigour are: water to form a second molecule of ethanoic acid; ammonia to form the primary amide ethanamide; ethanamine to form the secondary amide N-ethylethanamide.

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