Chem 124 Exam #3 Reaction Rules (Carboxylic Acids)

• Need a partial positive Carbon at end that you're going to extend (ex: C-Cl).
• THEN, just add CN^- , H⁺ , H₂O, w/u to add a Carboxylic Acid group on to the [new] end

*OR*

IF have a Br at end of chain that you want to extend (i.e. R-R-R-Br) then add an Mg (i.e. make the chain a grignard), then add a CO₂ w/ H⁺, H₂O, w/u to have the Grignard we made attach on this CO₂ as a Carboxylic Acid

You can add KMnO₄ , H₂O , H⁺ , Δ

*OR*

You can add NaOH to the partial positive Carbon (thus kicking off the Br and replacing it with OH (Sn₂) ==> making a primary alcohol) and then adding CrO₃ , H⁺

You can add BH₃ (which is a H^- source), H⁺ , H₂O , w/u

*OR*

• You can add LiAlH₄ , H⁺ , H₂O , w/u
• (remember the ⁺AlH₃ just gets grabbed by the O^- and makes the O leave, leaving a Carbocation which then gets attacked by the 2nd H^- from the LiAlH₄)

• You can add an alcohol (ex: CH₃OH) , H⁺
• (the HO-CH₃ just protonates the OH from the Carboxylic Acid and with the help of the resonating O^-, kicks out the OH, leaving behind an Ester)
• (remember that you'd rather have an OH^- in solution than a VERY unstable CH₃^-.. which is what CH₃Br's (Grignards) are)

*OR*

• (more tricky)
• Add an NaOH to the solution (which - being a "strong" base - will deprotonate the OH from the Carboxylic Acid, yield a Carboxide -- O^- hanging on the Carboxyl), then add a Grignard Reagent (e.g. CH₃Br) which has a +CH₃ that will get attacked by the O^- and get added onto the O^-, yielding an Ester!)

Just add an alcohol (R-R...-OH) with H⁺!

(the Alcohol that you add will attack the Carbonyl Carbon, then the H from the OH you added will transfer to the old alcohol, and the H⁺ will stabilize the Carbonyl O^-)

NaCN will turn an Alcohol into a Nitrile

Nitriles can be turned into Carboxylic Acids

H⁺ , H₂O will turn a Nitrile into a Carboxylic Acid

(side note: if you add a Base instead of an acid like we did above [ex: if you added NaOH], then you just turn the Nitrile into a Carboxide ion instead [COO-]).

• PBr₃ replaces an OH with a Br
• (this is useful for turning an Alcohol (OH) into a Grignard Reagent!)

• R..-CuLi simply replaces the Halide with whatever R..- is with the CuLi!
• (there has to be a Halide present however!)