Chap 21 Textbook slides

Chap 21 Textbook slides - CHAPTER 21 CHAPTER 21 Amines and...

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HAPTER 21 CHAPTER 21 Amines and Their Derivatives: Functional Groups Containing Nitrogen
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Naming the Amines 21-1 mines are related to ammonia in the same sense that ethers and Amines are related to ammonia in the same sense that ethers and alcohols are related to water. In the amines, the number of –R groups on the nitrogen atom defines the designation of primary, secondary and tertiary. Aliphatic amines are named as alkanamines according to Chem Abstracts. The name of the alkane stem is modified by replacing the ending – e with –amine.
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The position of the functional group is indicated, as in alcohols, by prefixing the carbon atom to which it is attached. Substances containing two amine functions are called diamines:
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Aromatic amines (or anilines) are called benzenamines. For secondary and tertiary amines, the largest alkyl substituent on nitrogen is chosen as the alkanamine stem. Other groups are named using N-, followed by the name of the additional substituent(s).
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An alternate naming convention is to treat the amino- functional roup as a substituent of the alkane stem group as a substituent of the alkane stem.
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Structural and Physical Properties of Amines 21-2 he alkanamine molecule is tetrahedral The alkanamine molecule is tetrahedral. The nitrogen orbitals in amines are very nearly sp 3 hybridized. The term pyramidal is often used to describe the geometry of the nitrogen atom and its three substituents.
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When an amine bears three different substituents (plus the lone pair of electrons), it has the potential to be optically active: At ordinary temperatures amines are not optically active, however because of a rapid isomerization process called inversion .
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The transition state for the inversion of an amine has been found to be between 5 and 7 kcal mol -1 for ordinary small amines. It is therefore impossible to keep an enantiomerically pure, simple di- or trialkylamine from racemizing at room temperature when the nitrogen atom is the only stereocenter.
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Amines form weaker hydrogen bonds than alcohols o. do. As a result, their boiling points are lower and their solubilities in water are lower. The boiling points of amines generally lie between those of the corresponding alkane and alcohol. maller amines are soluble in water (hydrogen bonding) Smaller amines are soluble in water (hydrogen bonding). When the hydrophobic part of an amine exceeds six carbons, the solubility in water decreases rapidly. Larger amines are essentially insoluble in water.
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Spectroscopy of the Amine Group 21-3 rimary and secondary amines exhibit a characteristically broad Primary and secondary amines exhibit a characteristically broad IR N-H stretching absorption between 3250 and 3500 cm -1 . Primary amines show two strong peaks in this range, whereas
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Chap 21 Textbook slides - CHAPTER 21 CHAPTER 21 Amines and...

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