rganic Chemistry otes by Jim Maxka C 24: Amines Topics Synthesis of amines ofmann Elimination Aryl amines Diazonium salts Connections: C C 2 2 2 C 2 2 2-3 - 2 2 2 C Ph- 2 Ph- Ph-C Ph- C24-1
rganic Chemistry otes by Jim Maxka All_about_amines Suggested Problems: 24:20-33, 39, 52 aming: Common names are formed from alkyl group the word amine. IUPAC drops e and adds amine. C 2 Label the amines as 1 o, 2 0, 3 0 or 4 0? What is 3 called? When the 2 group is a substituent, it is called amino like amino acid. ame these amino acids: Chirality: Properties and basicity: Amino acids are polar and can share -. So, some amines have higher boiling points. Which of the amines above do not bond to itself? The most important reaction is the basicity and nucleophilicity of the :. pka = 9-10 What is the base reaction for amide, - 2? Which is the stronger base? Aromatic amines are not as basic. Explain why the following are more than 10.000 times more acidic: 3 anilinium pka=5 pyridinium pka=5 C24-2
rganic Chemistry otes by Jim Maxka What is the relationship between acid strength and base strength? The carboxylic acid derivative amides are even less basic. Why? - C 3 M spectrum of -methylacetamide CM C24-3
rganic Chemistry otes by Jim Maxka Synthesis of amines: A. Exhaustive alkylation never leads to pure products except the 4 0 ammonium salt. 3 3 - Base 2 2 2 3 When an alkyl group attaches to an amine, the resulting substituted amine is more reactive. Why? B. In order to make specifc amines, we need indirect methods usually. To make primary amines, it is best to reduce an amide or nitrile. Benzonitrile LA acetamide LA Gabriel Amine synthesis: K - 2 C 2 - water C 2 - To make 1,2,3 0 amines, we can use reductive amination. Start with a ketone or aldehyde and make imine. Then reduce it. The most popular reducing reagent is ab (like B 4 but with a C). C 3 2-2 C 3 1. ab 2. acid workup - 2 2. acid workup C24-4
rganic Chemistry otes by Jim Maxka Skip ofmann and Curtius rments. ext to reactions: emember that amides are made from other carboxylic acid derivatives: ow could you make acetamide from ethanol? 2 ( ) 3 Aryl amines: Aryl amines are not as basic as alkyl amines and show substituent effects. Last the ofmann elimination gives the non-zaitsev product: ere is an example of sec-butyl amine Ag 2 in base. C MeI excess 2 - least substituted 2 Three ways to synthesize aniline: 1. benzyne 2. Zn/ reduction of nitrobenzene 3. AS with EWG in o,p group. Arylamines and EAS: emember some o,p patterns were easy, but meta was tricky. Let s review a little. We could easily make p-bromoaniline by this path: But how to make meta-bromoaniline. Both bromo and amino are o,p directors. Well start with nitration. Then brominate. Then, reduce the 2 group. Voila, putting it all together. We can do a lot better because the 2 group can be turned into many different groups through transformation into the diazonium salt. emember some o,p patterns were easy, but meta was tricky. Let s review. We could easily make p- bromoaniline by this path: 2 2 /Fe 3 2 ortho C24-5
rganic Chemistry otes by Jim Maxka But how to make meta-bromoaniline. Both bromo and amino are o,p directors. Well start with nitration. Then brominate. 3 / 2 S 4 2 /Fe 3 2 Then, reduce the 2 group. Voila, putting it all together. 2 Zn, 2 2 We can do a lot better because the 2 group can be turned into many different groups through transformation into the diazonium salt. - made from - 2 and a 2 (nitrite) in Diazonium reaction: Formation of the Diazonium salts: Sandmeyer type reaction: The diazonium salt makes the world s best LG = 2 (g). Start with aniline and react with nitrous acid ( 2 not nitric) followed by dehydration under acidic conditions: 2 : - 2 - - - - 2-2 - 2-2 - The diazonium can react with Cu to substitute for 2 or hydroysis to make phenol or 3 P 2 to make. For or a, Cu; u = F,,, I, C u: For Cu 2, 2 u = For ypophosphorous acid u = - u 2 General procdure for meta substitution for o,p directors. 2 2 M 3 Sn 2 a 2, 2 u: - 2 u For or a, Cu; u = F,,, I, C For Cu 2, 2 u = For ypophosphorous acid u = C24-6