week6_questions (Key)

week6_questions (Key) - Chemistry S-20 Week 6 Amine...

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Amine Basicity N NH C N N N N Cl CH 3 CH 3 N N N N Me 2 N 1. Rank each of the following sets of nitrogen bases in terms of basicity, and explain your ranking: most basic least basic most basic most basic most basic least basic least basic least basic sp 2 hybridized sp hybridized sp 3 hybridized The –OH is the most electronegative "substituent" which makes it less basic. Note that -OH is not capable of donating into a pi system here. The –NH 2 acts as an electronegative "substituent" on the other –NH 2 . Note that -OH is not capable of donating into a pi system here. –CH 3 groups are electron donating –Cl is electron withdrawing The other "N" acts as an electron-withdrawing substituent The Me 2 N is electron donating (by resonance). Protonation takes place on the N in the ring. H 2 NNH 2 NH 3 HONH 2 N N N CH 3 CH 3 most basic least basic aromatic lone pair not in conjugation (can't violate Bredt's rule.) Chemistry S-20 Week 6 188
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Amine Synthesis: Reagents 1. 3. 1. 3. 1. 1. Each of the following transformations can be carried out in one to three steps. Fill in the reagents required for each step. Br NH 2 O HN O Cl N O 3. HO NH 2 1. 3. NH 2 1. 3. H 2 ,Pd H 2 N (could also use Gabriel synth) pH 5 , NaBH 3 CN HN LiAlH 4 H + workup HNO 3 ,H 2 SO 4 Sn , HCl NaCN, HCN NaN 3 2. 2. 2. 2. 2. LiAlH 4 H + workup Chemistry S-20 Week 6 189
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