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Unformatted text preview: Amines 1 Copyright, Arizona State University Copyright, Arizona State University Amines Organic Bases • trivalent, but tetrahedral N 1° Amine 2° Amine 3° Amine Quaternary Ammonium Salt R H H N R R' H N R R' R'' R 1 N R 2 R 3 R 4 1 Nomenclature IUPAC priority: acid > ester > amide > nitrile > aldehyde > ketone > alcohol > amine > alkene > alkyne > halide • named as for alcohol, replace -ol with -amine CH 3 CH 2 CH 2 NH 2 1-propanamine (2S)-pentanamine NH 2 N-ethyl-1,N-dimethyl-1-propanamine longest chain C O OH N 3-(dimethylamino)propanoic acid Named as substituent, lower priority 1 2 3 substituent N CH 2 CH CH 3 CH 3 H 3 C CH 2 CH 3 C O HO NH 2 m-aminobenzoic acid Br NH 2 3-bromo-2-chloroaniline Cl Me N Et Me Pr Cl ethyldimethylpropylammonium chloride • some amines with common names diethylamine diisopropylamine aniline NH H N NH 2 H N pyrrolidine putrescine benzylamine NH 2 H 2 N NH 2 NH 2 H 2 N cadaverine H N pyrrole (amines can stink!) 1,4-diazabicyclo[2.2.2]octane (DABCO) N N N N pyridine 2,6-lutidine Amines 2 Copyright, Arizona State University • amine base components of RNA and DNA N H N cytosine (C) NH pyrimidine bases O N H NH thymine (T) O O H 3 C N H NH uracil (U) O O HN N N N H guanine (G) H 2 N O N N N N H adenine (A) NH purine bases I won't test you on these!!! 2 Amines as Bases • deciding the stronger of two acids, e.g. H-A 1 and H-A 2 H A 1 H + + A 1 – H A 2 H + + A 2 – • the stronger acid has the more stable anion • the stronger acid corresponds to the more favorable "reaction", left to right • deciding the stronger of two bases, e.g. B 1 and B 2 B 1 B 1 –H B 2 B 2-H + H + + H + • there are no anions here, but the stronger base STILL corresponds to the more favorable reaction Example + H + + H + more stable cation less stable cation weaker base stronger base more favorable less favorable D group, raises energy of electrons on N, more reactive W group, lowers energy of electrons on N, less reactive D group stabilizes positive charge on N W group destabilizes positive charge on N R N R H H 3 CO R N R H O 2 N R N R H 3 CO R N R O 2 N • measure basicity in terms of acidity (pKa) of conjugate acid (we will not use the pKb scale) Amine a c i d strength + H 3 O NH 3 pKa ~35 weak acid NH 2 strong base + H 2 O • compare (and don't confuse!!) Amine b a s e strength + H 3 O NH 4 pKa ~9 moderate acid NH 3 moderate base + H 2 O Amines 2 Copyright, Arizona State University • amine base components of RNA and DNA N H N cytosine (C) NH pyrimidine bases O N H NH thymine (T) O O H 3 C N H NH uracil (U) O O HN N N N H guanine (G) H 2 N O N N N N H adenine (A) NH purine bases I won't test you on these!!!...
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- Spring '12
- Bases, Amine, H3C