CHEM 302 S09 CA8 key

CHEM 302 S09 CA8 key - CHEM302, Spring 2009 Dr. Ruder 1...

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CHEM302, Spring 2009 Dr. Ruder 1 Class Activity 8 Amines Model 1 : Basicity of Amines NH 2 N H H H NH 2 N H N pKb=4.74 pKb=3.36 pKb=3.01 pKb=3.24 pKb=9.4 2º alkyl 3º alkyl 1º alkyl ammonia 1º aryl Questions: 1. Consider the amines shown in Model 1. (a). Identity the amines as alkyl or aryl. See above (b). Identify the amines as 1º, 2º or 3º. See above 2. A low pKa value indicates a strong acid. What does a low pKb value indicate? A low pKb indicates a strong base. 3. From the information in Model 1, identify which compound is the strongest base and which compound is the weakest base. Et2N is the strongest base, aniline is the weakest base. 4. Using the general classification of amines (ammonia, 1º, 2º or 3º), rank from strongest to weakest using the data in Model 1. Make sure everyone in the group agrees with this ranking. 2º>3º>1º>NH 3 Model 2: Amines as Bases CH 3 NH 2 + H-O-H CH 3 NH 3 + + HO- Questions: 5(a). In the reaction shown in Model 2, identify the acid, base, and conjugate acid/base. Draw curved arrows to indicate electron flow. See above (b). Draw the product that results when dimethylamine reacts with water. (c). Compare the products from methyl amine (1º) and dimethylamine (2º). Which product is more stabilized by induction? Explain. Draw polarity arrows on the C-N bond to show this inductive effect. Alkyl groups donate electrons by induction, so the conjugate acid of the secondary amine is the most stabilized. (d). Draw the product when trimethylamine reacts with water. Is this product more or less stabilized by induction compared to the 1º and 2º amines shown above? A 3º amine is more stabilized by induction . (e).
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This note was uploaded on 02/17/2011 for the course CHEM 302 taught by Professor Ruder during the Spring '09 term at VCU.

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CHEM 302 S09 CA8 key - CHEM302, Spring 2009 Dr. Ruder 1...

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