Oxidation of alcohols Chromic Acid KMnO4 PCC Swern 1 ROH RCOOH RCOOH RCHO RCHO 2 ROH Ketone Ketone Ketone Ketone 3 ROH NR NR NR NR

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1 Chapter 11 xidation in rganic terms xidation Reduction Neither Addition of, X2; loss of 2 Addition of 2; loss of or X2 Anytime you oxidize one carbon but reduce another (ex. Adding and to adjacent carbons) xidation of alcohols Chromic Acid KMn4 PCC Swern 1 R RC RC RC RC 2 R Ketone Ketone Ketone Ketone 3 R NR NR NR NR Why don t you oxidize 3 alcohols? [] 5 bonds to carbon=crazy talk! You won t need to draw the structure of PCC, but you do need to recognize it. N Cr pyridinium chlorochromate (PCC) You don t need to know all the reagents of Swern xidation for Mr. Baker s class. Tollens Test Not tested in this course. o Qualitative test for aldehydes o Aldehyde AgN3 Carboxylic acid silver metal o If you see the silver metal coating the tube, then you know you have an aldehyde. NAD /NAD o You need to know the structures of both! o NAD is the oxidized form/oxidizing agent

2 N2N N sugar o NAD is the reduced form/reducing agent N2 N sugar Formation of Tosylates R S S a sulfonyl chloride tosyl chloride (a specific sulfonyl chloride) o Addition of tosyl chloride (Ts) converts the hydroxyl into a good leaving group ( - Ts) with retention of stereochemistry. - Ts is a weak base Ts Ts o Recognize that any sulfo nyl chloride will do this o You don t need to draw out the entire structure when you use tosyl chloride to make a tosylate You do need to draw out the entire structure when you use a different sulfonyl chloride to form a sulfonate. F3C S S CF3 o The RS3 - is a very weak base, so it s an excellent leaving group.

3 o That s it! Don t stress out over this. Reacting with X o The hydroxyl is protonated. Water falls off, leaving a carbocation intermediate Carbocations rearrange! o The halide ion attacks the carbocation. o With 1 alcohols, this reaction occurs through an SN2 mechanism. Specialty Reagents o PX3, PX5, and S2 all replaced hydroxyl groups with halogens Sometimes you ll just see phosphorus and bromine (or P/I2) here. Think flexibly. It makes PBr3 (PI3). Don t worry about mechanism or stereochemistry here. S2 works better than P3 and P5. o That s it! Dehydration of alcohols o Protonate the hydroxyl, water falls off, leaving a carbocation 2S4 3P4 o Eliminate in both directions

4 o Look to see if the original carbocation can rearrange o Again, eliminate in all directions Formation of symmetrical ethers industrial dehydration of alcohols o First, the hydroxyl group is protonated, creating a good leaving group. o Then, another alcohol comes along and kicks off the water in an S N2 mechanism. o The reaction is finished off with the deprotonation of the oxygen. o Favored at reasonably hot temperatures (140 C), because higher temperatures would favor elimination o Works best on primary and methyl alcohols. It is an SN2 after all! o If you try to make asymmetrical ethers this way, you will get a mixture of products. Because you get a mixture of products, you can call this a low-yield reaction. Pinacol Rearrangement a reaction of vicinal diols o First, the hydroxyl group is protonated (see a pattern here?)

5 o Then water falls off. o A methyl shift happens because the resulting carbocation is resonancestabilized. The resonanc e form with the positive oxygen is the most stable because of the octet rule. o Finish it off by deprotonating the oxygen! o This reaction occurs with other vicinal diols as well, so don t expect it to just be pinacol on the quiz or test. Mr. Baker always gives you symmetrical molecules for this reaction, so it doesn t matter which hydroxyl you protonate in the first step. If you were given an asymmetrical molecule then you would get a mixture of products. o To get to the product without thinking about the mechanism: Make one of the s into a carbonyl. Put two methyls where they other hydroxyl was.

6 Periodic Acid eavage of Vicinal Diols o Just cleave the bond between the two carbons and turn the alcohols into carbonyls. I4 o Do not further oxidize aldehydes to carboxylic acids. Fischer Esterification o This is a big one to know! ACS, MCAT, DAT, PCAT, AT, etc. will expect you to know this! o verall: Carboxylic acid alcohol ester water o Step 1: protonation of carbonyl to activate it for attack. o Step 2: Alcohol attacks carbonyl carbon of the acid o Step 3: Deprotonation of the oxygen from the alcohol o Step 4: Protonation of one of the oxygens from the acid o Step 5: Loss of water, forming a resonance-stabilized carbocation

7 o Step 6: Deprotonation of carbonyl Esters of inorganic acids o Just take an acid that isn t a carboxylic acid (phosphoric, sulfuric, etc) and add an alcohol to make a different type of ester. N3 N2 N2 N2 glycerine nitroglycerine o Know that DNA and RNA are polymers with a phosphate ester in there. Williamson Ether Synthesis o Just an SN2 with an alkoxide as the nucleophile. o Remember that you want the substrate to be either methyl or primary. An alkoxide would abstract a proton from a 2 or 3 substrate, in an E2 mechanism o Ex. ow would you synthesize the following ether from two alcohols? o Answer: Ts Ts Na

8 Ts