#ohem

My #MondayMantra ~ 

Nah, not gonna tell you how to brew.  Cause honestly I don't even drink, but this is the alcohol chapter so lots of drinking jokes, savvy? 

I am going to tell you how to make alcohols in a lab, though.  Hopefully in the process I'll remember this for myself.  I'm not really going to cover mechanisms, because I don't need to know them for the final, but if I ever do I think you'll be entertained.  I find that mechanisms are way easier to remember if you look at them like they are a drama series on TNT.  

I'm going to emphasize reagents because, trust me, memorizing reagents is the way to go.  If you try to remember specific chemicals will be the death of you.  If something is a reducing agent, then it just adds H's.  If it's a really strong reducing agent, it adds H's all over the damn place.  Here an H there an H everywhere and H H.  It's like, shit, REDUCE ALL THE BONDS! ABANDON SHIP H'S! Some reducing agents are so strong that the Os run away too, out of sheer awe.  No, just kidding, but strong reducing agents do remove the O and take something straight down to the alkane.  BORING.  

One last note: Because this is a computer and I can't draw arrows like in reactions, here's how I format/notate them: reagent, reagent is on the same side (top or bottom) of an arrow.  If it's on the bottom of the arrow, I'll do a / between.  So a lot of times it looks like: reagent, reagent/reagent.  If it's multistep, I'll say that too.  

1. Hydration of an Alkene.  Double bond do shit, right? So if you add water, some protons (an acid, really.) and heat, you can make alcohols.  Only 1 or 2 degree though, because how could you have a double bond on a carbon that's tri subbed? You can't, that's how.  Carbons don't make 5 bonds, they make 4.  Important things to know: This does have a carbocation intermediate (which, if I can call your attention to it, is that molecule that happens when you rip off part of it and it has a weird charge.  It's fairly stable, which means it hangs around long enough to do chemical things.).  Markovnikov is invoked (He's the guy that says that things land on the most heavily substituted C.), but this isn't a very favorable reaction.  Probably because of the heat.  Ochemists don't like heat because our chemicals tend to blow up.  Pardon me, they tend to participate in some very exothermic degradation reactions.)

2. Hydration of Alkene by Oxymercuration/reduction - This is a two-step reaction, and the first reagent is Hg(OAc)2 over H2O.  Any time you see mercury it's always oxymercuration, and it usually involves a bond breaking somewhere.  So the first product has the HgOAC attached to on side of the bond, and the OH on the other.  This makes whatever is there chiral (recall you some chiral chemistry.  Or, rather, don't, because it's a giant pain in the ass.  Really you can just remember innie and outie.  R/S if you're feeling fancy.  Cis/Trans if you're lucky enough that your molecule is simple.).  The second reagent is NaBH4.  The result is a 1 or 2 degree ROH that's chiral.  Markovnikov is invoked.  To put it succinctly: Hg breaks the bond, and then we add OH across it.  

3. Hydration of Alkene by Hydroboration/oxidation - Another two step reactions.  The reagents for the first part are: BH3/THF, and for the second part are: H2O2/OH-.  The result is a chiral OH created over the bond.  Remember, even though we don't really care about them, the Hs are chiral, too, and anything that was subbed on either side of the bond is also chiral.  It just makes everything pop in and out of the page.  We don't really care about the Hs when naming it though, so sometimes you can go with Cis/trans.  Well, Trans, because it'll never be Cis with the thing on the other side of the bond.  It is _NON_ Markovnikov.  

TBH, your teacher probably won't ask you much about these, so in (pre)med student speak they are generally low yield for studying.  The reason is that a, they're boring and b, the other methods will show up in other chapters on the "reaction" side instead of the "creation" side.  So when we, say, reduce a carbonyl? That also shows up in the carbonyl chapter.  These will never be repeated this semester, they are part of 1st semester ochem.  

4. Reduction of Carbonyl Compounds - These are high yield for studying.  You'll see them over and over because they are super common.  And much less boring.  You know, as much less boring as ochem can be.  

     a. Red. of Aldehydes to 1 degree OH - Obviously, an aldehyde can only be a 1 degree ROH because Aldehydes are on the end of the chain.  The reagents are: NaBH4, EtOH/H3O+.  Alternatively, it can also happen with LiAlH4, Ether/THF.  This is actually more reactive, but LiAlH4 causes cancer and is super poisonous (ISN'T OCHEM FUN KIDS???) so we try not to use it unless it's actually necessary.  

     b. Red of Ketones to 2 degree ROH - Obviously, Kets can only be 2 degree ROH because they're in the middle of the chain.  If they weren't, they'd be Aldehydes.  If you're having trouble remembering which is which, just remember that the letter A bookends the alphabet, and K is in the middle.  See? I'm so smart.  *horn toot* (no not really.).  Also, formaldehyde: the only ketone that's also an aldehyde.  It's like it couldn't make up it's mind, and also is a necrophiliac.  

Shit i am getting off the point.  

Reagents: NaBH4, EtOH/H3O+ or LiAlH4, Ether/THF.  You'll notice the striking similarity here to the aldehyde.  This isn't the first time that you'll see kets and alds behaving similarly.  They do that a lot, but not ALWAYS.  It might be easier to memorize the reactions that they do differently and then only memorize the other ones once.  

     c. Reduction of an Ester to a 1 degree ROH - Again, makes sense, because to turn and ester into an alcohol you need to knock the hydrocarbon off of the side of it (Esters, kiddies, not ethers.  Ethers are boring and do almost nothing.  They're so boring that they're solvents for things that are far more interesting than they are.  Also, never huff them in lab it might turn out to be a poor life choice.  Unless you like passing out, IDK.  Esters, on the other hand, usually smell kind of sweet and fruity and smelling them is a slightly less poor life choice.).  

Off topic again.  I am tired, sorry, and I really wish I had some caffeine on hand.  

Reagents: LiAlH4, ether/H3O+  You cannot use anything else, because you don't want to reduce the thing back to the stone age.  Also, noticing a pattern here? LiAlH4 is a reducing agent.  It's purpose in life is to give away Hs.  I suppose that makes it an acid too strictly speaking, but it really prefers the sportier name of reducer.  Important: This produced *two* 1 degree OHs.  One from each side of the bond with the O, so it's advisable to use an ether thats a diether (IE, dimethyl ether, or diethyl ether).  When the molecule gets cut in half both sides will be the same, so you'll have more product.  Otherwise you'll have to separate them, and you're an ochem student.  You know what a pain in the ass that is.  

     d. Red of COOH to a 1 degree ROH - I'll give you three guesses as to the reagent, and the first two don't count.  Yeah.  LiAlH4, Ether/H3O+.  This is another case where we want to stick with that, so that we don't reduce this thing back to the stone age.  No other bonds in it are reduced, just the C=O.  This is a case where the reducer is strong enough that the O runs away in fear and you're just left with the OH part of a COOH bond.  SPIFFY.  Remember, though, LiAlH4 is dangerous so use it only when you need to.  Or if you like danger and wasting expensive chemicals.  WHICHEVER.  

5. GRIGNARD BITCHES - THIS IS HIGH YEILD.  If you can't remember the Grignard reaction then you just slept through all of second semester ochem.  This is used a lot, because it's really useful.  Ok, so, check it out.  To make a grignard reagent you add Mg to a halide of any variety.  Ok? Ok.  This gives you an R-MgX.  R, of course, being the hydrocarbon of any random type (but unsubstituted, because the grig is REALLY reactive and we don't want it to cannibalize itself.  So don't think you can turn a ketone or something into a grig, cause you can't, it just reacts with itself. CANNIBAL.), and X being a halide of any type (Cl or Br being the most common.).  

     - If you add a ketone to a grig, you get a 3 ROH.  This makes sense because, as we recall, ketones are in the middle of the chain.  They already have two things attached to them.  So when you add the other hydrocarbon chain, you're adding a 3rd thing.  The ROH forms at the site of addition (on whichever C the O was bonded to), so we get a 3 degree ROH.  

     - If you add it to an Aldehyde, we get a 2 degree ROH.  Again, makes sense if you think about it because an aldehyde is attached to on thing already, and the grig attaches its R group, so you get a 2 degree ROH.  

    - Formaldehyde, you saucy minx you, is the only way to make a 1 degree ROH with the grig.  

    - If you add it to and Ester, you also get a 3rd degree ROH because the reaction uses *two* moles of grig.  It attaches twice, and it cuts off the other section of the Ester.  So you get two kinds of OHs from this, the 3rd degree one and a 1 degree one.  It's a weird rxn that you don't see that often because of the mixed product.  See "no one likes separating products" for reasons.  

Some other notes about the Grignard: It can be hindered by certain functional groups being present on a molecule (remember where I said you can't make a grig out of things with functional groups?).  It will self protinate if these are present: -OH, -NH, -SH, -COOH.  Basically anything with an H.  See? H, protinate...makes sense, right? =D If these groups are present, it reacts with itself: Ald, Ket, C=ONR, Nitriles (C triple bond N), -NO2, SO2R.  

     *When I say "present" I mean "on the thing that you're trying to turn into a R-MgX, which is the actual grignard.  I am not talking about on the thing you're reacting it with, although grigs don't work with weak bases, so it won't work with an NH group of some type present.  

Also, last note about the grig, if you try to react it with a COOH it does not do the hydrocarbon addition reaction, it makes a COO-MgBr salt, with an RH mixed.  It's...sort of? Useful.  We'll revisit that when we get to COOHs.  There's three whole chapters on those things.  

So if your teacher asks you to name some ways to prepare an alcohol, you can say: 

1. Reduction of Ketones, aldehydes, and COOH groups.  

2. Addition of an OH across a double bond, otherwise known as Hydration (cause we're adding water, OH to one side and H to the other.  See? H2O).  

3. Grignard reactions.