water related

water related思维导图，包括：Dehydration和hydration两部分内容，喜欢的小伙伴可以点个赞哦！

water related

• Dehydration
  • dehydration of primary amide
    • with Thionyl chloride (SOCl2)
    • Gnerate nitriles
    • mechanism. Socl2 nucleophylic attack, followed by E2 like
  • Imine and Enamine formation(Nu addition followed by dehydration)
    • Imine R2=NR
      • neucleophile is primary amines
      • ex. Schiff base in our body
        • can produced by Alanine react with PLP
          • a common way of its metabolism
      • nitriles can added by grignard reagent to yield Imine ion, then it adds a water to yield a ketone, by a machanism that is exact reverse of immine formation
        • p626
    • enamine R2N-CR=CR2
      • neucleophile is secondary amines
  • dehydration of alcohol
    • products
      • C=CR2
        • by reactants
          • 3' alcohol
        • trearment
          • H3O+
          • E1
      • C=C
        • by reactants
          • 2' alcohol
          • 3' alcohol
        • treatment
          • POCl3
          • Pyridine
          • E2
      • E1Cb in biological system
      • Followed zaister's rule: major product is more stable alkene, due to C+ rearrangement
  • dehydration after adol reaction
    • between β-hydroxyl group and α-hydrogen
    • generate conjugated enones or α，β-unsaturated products
      • they have sharing pi electrons system/ holistic pi MO
        • more stable than nonconjugated enones
        • just like conjugated diene
    • condition
      • basic
        • E1cB
        • through enolate ion
      • Acidic
        • E1/E2
        • through enol
      • temperature
        • a bit higher than idol formation
          • hard to isolate adol, usually the product of carbonyl condensation
    • Value
      • move the idol formation equilibrium to product
        • removal of water
        • even though the initial equilibrium is unfavored
  • Hemiacetal dehydration to oxonium ion(C=O:+-R)
    • acid protonates hemiacetal's hydroxyl group, it then leaves to gave oxonium ion
    • double bond of oxonium ion is then added by another alcohol
    • water deprotonate the added alcohol, regenerate H3O+
    • yield actetal
    • definately reversiable
  • usually E1,E2,E2like,E1cB: depends on substrate and nucleophiles you applied
    • often convert -OH a better leaving group
      • protonation by acid
      • or substitute it by another group
• hydration
  • hydrolysis
    • all acyl derivatives exept carboxylic acid can undergo hydrolysis
      • anhydride hydrolysis: 2 acids
        • direct add H2O, with out catalyst, so does below
        • we usually use bases such as pyridine or NaOH to neutralie generated HCl
      • acid chloride hydrolysis: acids
        • hydrolysis(react with water)
          • direct add H2O, with out catalyst, so does below
          • we usually use bases such as pyridine or NaOH to neutralie generated HCl
      • ester Hydrolysis: acids
        • Hydrolysis base catalyst
          • in base called sponification
          • yildes alkoxide ion and carboxylic acid
            • but alkoxide ions immediately deprotonate carboxylic acid
              • so may treat with aqueous acid if you want carboxylic acids
          • isotope labbling prove the nucleophilic acyl substitution mechanism
        • hydrolysis with acid catalyst
          • Usual mechanism: reverse of ficher esterification
            • acids first activated for nucleophilic attack by protonation of acid's carbonyl oxygen
            • then alcohol attacks the carbonyl carbon
            • The scond internal proton transfer transfer -OH2+'s proton to -OR oxygen make it a better leaving group
          • Enzyme mechanism: 2 sequential neucleophilic attacks
            • 1. transesterification to give a acyl enzyme
              • with tetrahedral intermediate
            • 2. hydrolysis to give an acid and free enzyme
              • with tetrahedral intermediate
            • both step requires general acid catalysts to make leaving group leave
      • ester hydrolysis: acids +ammine
        • similar(basically same) with ester acid/base catalyzed hydrolysis
          • base catalyst is hard because it can't protonates -NH2 to make a better leaving group
            • reversible
              • equilibria shifts by base deprotonates acids product
          • acid catalyst also followed by internal proton transfer
            • reversible
              • equilibria shifts by catalyst protonates NH3 product
          • but both requires heating in aqueous acid/ aqueous base
          • Biological enzyme catalysts cleavage
            • identical with ester cleavage with acyl enzyme intermediate
      • Hydrolysis
        • all nucleophilic acyl substitution can catalyst by both acid/base
          • but base can't accelerate the leaving step
    • Nitriles to carboxylic acid
      • p 625
      • first hydrolysis to amide
        • through a imine anion intermediate
        • mechanism: nucleophylic addition
          • just like other hydration, can be catalyst by acid/base
      • second hydrolysis to carboxylic acids
        • mechanism: nucleophylic acyl substitution
        • but only produce carboxylate ion, for reason of NH3 formation, so need further acidification
  • ketone/aldehyde hydration(form germdiols)
    • Catalysis
      • Acid catalysis mechanism
        • protonation of Carbonyl oxygen makes the carbonyl carbon more electrophilic
        • Water deprotonates the protonated diol intermediate then regenerates acid catalyst
      • Base catalysis mechanism
        • hydroxide ion is more nucleophilic than water
        • water protonates alkoxide ion then regenerates hydroxide ion
    • highly reversible
    • form germdiols
  • usually nucleophylic addition: catalyzed by both acid/base
    • the reverse is dehydration
      • like actetal formation
    • alcohol mimics water with same mechanism
      • ester formation
      • hemiacetal-actetal formation