Nitrogen containing organic compounds
Nitrogen containing organic compounds Lecture-5
Reactions
A g + \mathrm{Ag}^{+} Ag + R + \mathrm{R}^{+} R + A g X p p t \mathrm{AgX} \hspace{1mm} \mathrm{ppt} AgX ppt
N u − Nu^- N u −
Reactions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow →
Nitrogen containing organic compounds Lecture-5
Reactions
Reactions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow →
Nitrogen containing organic compounds Lecture-5
Walden inversion
Reactions → \rightarrow → Walden inversion → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow →
Nitrogen containing organic compounds Lecture-5
Nucleophilic substitution
Nucleophilic Substitution at a saturated carbon:
Nucleophile
It is an electron rich species reacts with an electron poor species
Nucleophilic substitution
One nucleophile replaces another
It occurs when an electron rich species the nucleophile reacts with an electrophilic saturated C-atom
Which is attached to a electronegative group (important), the leaving group
Reactions → \rightarrow → → \rightarrow → Nucleophilic substitution → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow →
Nitrogen containing organic compounds Lecture-5
Nucleophilic substitution
Reactions → \rightarrow → → \rightarrow → Nucleophilic substitution → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow →
Nitrogen containing organic compounds Lecture-5
Discrete mechanisms
S - Substitution
N: Nucleophilic
1: unimolecular
Reactions → \rightarrow → → \rightarrow → → \rightarrow → Discrete mechanisms → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow →
Nitrogen containing organic compounds Lecture-5
Discrete mechanisms
S - Substitution
N: Nucleophilic
2: Bimolecular
Reactions → \rightarrow → → \rightarrow → → \rightarrow → Discrete mechanisms → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow →
Nitrogen containing organic compounds Lecture-5
Discrete mechanisms
Reactions → \rightarrow → → \rightarrow → → \rightarrow → Discrete mechanisms → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow →
Nitrogen containing organic compounds Lecture-5
Discrete mechanisms
Both alkyl bromide and OH are participating in the rate - limiting (slowest) step of the reaction
OH becomes partially attached to carbon before Br is fully detached
Energy necessary for breaking C-Br bond is supplied by that produced in forming HO-C bond
Quantum mechanical calculation shows that an approach by OH along the line of centers of the C & Br is that of lowest
Reactions → \rightarrow → → \rightarrow → → \rightarrow → Discrete mechanisms → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow →
Nitrogen containing organic compounds Lecture-5
S N 2 S_N2 S N 2
Reactions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S _N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S _N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow →
Nitrogen containing organic compounds Lecture-5
Reactive intermediates
Reactions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → Reactive intermediates → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow →
Nitrogen containing organic compounds Lecture-5
Structure
Reactions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → Structure → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow →
Nitrogen containing organic compounds Lecture-5
Structure
Reactions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → Structure → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow →
Nitrogen containing organic compounds Lecture-5
Important point to remember
Inversion of configuration does not mean R going to S or vice versa. It means that bond formation takes place opposite to that of bond breaking …….. which leads to the inversion
It is like inversion of umbrella in a storm
Reactions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → Important point to remember → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow →
Nitrogen containing organic compounds Lecture-5
S N 2 S_N2 S N 2
Reaction profile diagram for S N 2 S_N2 S N 2
Reactions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow →
Nitrogen containing organic compounds Lecture-5
Reaction
Halide undergoes slow ionization to yield the loan pair R + R^+ R + C l − Cl^- C l − O H − OH^- O H −
The energy neccessary to effect the initial ionization is largely recovered from the energy envolved through solvation of the resultant loan-pair
Reactions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → Reaction → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow →
Nitrogen containing organic compounds Lecture-5
Reaction
Factors Affecting the Rate of S N 1 S_N 1 S N 1 S N 2 S_N 2 S N 2
The structure of the substrate
Concentration and reactivity of nucleophile (for biomolecular reactions only)
The effect of solvent
The nature of leaving group (nucleofuge)
Stereochemical implications of mechanism
Reactions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → Reaction → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow →
Nitrogen containing organic compounds Lecture-5
Effect of substrate
Substituent
Compound
Relative Rate,k 2 k_2 k 2 S N 2 S_N 2 S N 2
Relative Rate, k 1 k_1 k 1 S N 1 S_N 1 S N 1
Methly
H 3 C − X H_3 C - X H 3 C − X 6 × 10 3 6 \times 10^3 6 × 1 0 3 0.002
1 o 1^o 1 o H 3 C H 2 − X H_3 CH_2 - X H 3 C H 2 − X 30
0.004
2 o 2^o 2 o ( H 3 C ) 2 H C − X (H_3 C)_2 HC - X ( H 3 C ) 2 H C − X 1
1
3 o 3^o 3 o ( H 3 C ) 3 C − X (H_3 C)_3 C - X ( H 3 C ) 3 C − X 0.00005
4 × 10 6 4 \times 10^6 4 × 1 0 6
Reactions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → Effect of substrate → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow →
Nitrogen containing organic compounds Lecture-5
The synthesis of amines by reduction methodologies
Reduction of Nitro Compounds
Anilines may be prepared by reduction of nitrobenzenes. The overall synthetic begins with nitration of the starting arene
Reactions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → The synthesis of amines by reduction methodologies → \rightarrow → → \rightarrow → → \rightarrow →
Nitrogen containing organic compounds Lecture-5
The synthesis of amines by reduction methodologies
The Dissolving Metal Reduction of Nitrobenzenes to anilines
These reactions use metals such as iron, zinc and tin and typically are carried out at reflux in hydrochloric acid solution, sometimes with added acetic acid to help dissolve the aromatic compound
Example:
Reactions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → The synthesis of amines by reduction methodologies → \rightarrow → → \rightarrow → → \rightarrow →
Nitrogen containing organic compounds Lecture-5
The synthesis of amines by reduction methodologies
Reactions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → The synthesis of amines by reduction methodologies → \rightarrow → → \rightarrow → → \rightarrow →
Nitrogen containing organic compounds Lecture-5
Catalytic Hydrogenation of Nitroaromatics
Anilines may also be prepared by catalyzed reaction of pre-formed hydrogen with nitroaromatics:
Reactions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → Catalytic Hydrogenation of Nitroaromatics → \rightarrow → → \rightarrow →
Nitrogen containing organic compounds Lecture-5
Reductive amination
Aldehydes and ketones can be converted into amines by catalytic or chemical reduction in the presence of ammonia or a 1 o 1^o 1 o 2 o 2^o 2 o
These conversion can alternatively by viewed as reductive alkylations of the starting amines
Reactions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → Reductive amination → \rightarrow →
Nitrogen containing organic compounds Lecture-5
Structure
Reactions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → Structure
Nitrogen containing organic compounds Lecture-5
Structure
Reactions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → Structure
Nitrogen containing organic compounds Lecture-5
Structure
Reactions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → Structure
Nitrogen containing organic compounds Lecture-5
Structure
Reactions → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → S N 2 S_N2 S N 2 → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → → \rightarrow → Structure
