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CHEM 30BL: Organic Chemistry Laboratory I Final Study Guide

Part 1 | Part 2 | Part 3 | Part 4

Hey, everybody! I’ve decided to post a link to a google drive that contains notes from my Calculus I and II and my Organic Chemistry I and II classes. I earned good grades in these classes and I hope these notes can help you guys do that too! The notes are arranged by date and they are also labelled with topics. I apologize for any mistakes that may be found. If you find something really erroneous, shoot me a message with the class and date and I’ll try to fix it when I get the chance.

If you found my notes useful, please reblog so that more people can see it! Happy studying!

Shaysstudies’ Google Drive

P.S. All of the notes have been revised and edited to look nice except for those in the Calc I folder. If I get the opportunity, I am going to rewrite and re-post them.

lexhasadragon

Very Fast Study Tip™

If you are a university student, especially a STEM major, ESPECIALLY AN ORGANIC CHEMISTRY STUDENT, you need a whiteboard.

You can revise all the notes in your respective hemisphere but without active repetition it means nothing. Write your mechanism/structure/wedding vows. Erase part of it. Write it again. Erase more of it. Repeat.

Get a big one so that you can sit on the floor/bed/table without straining your back from looking down. I have no attention span but I can white-board for hours.

productivepls

PLA DO THIS

cyclicstudies

Organic Chemistry: Electrophilic Additions to Alkenes

Hey all! I wanted to put together a few review guides for the reactions I learned in my organic chemistry 1 class. I’m starting off with the alkene-related reactions, specifically with electrophilic additions. Despite being super hard to fully conceptualize (I still have trouble with them!!), they’re very important to recognize, because the same patterns repeat with other reaction types, particularly with alkynes. I’ll go through each reaction type here with a quick mechanism and jot down important bits of info. But before I start, I used a lot of abbreviations, so here’s a key:

R+ is carbocation

R is any group with a carbon

IM is intermediate

X is halogen

E+ is electrophile

RDS is rate-determining step

HOMO is highest occupied molecular orbital

LUMO is lowest unoccupied molecular orbital

Squiggly lines indicate enantiomers formed due to alternating wedges and dashes

Addition of HX

Introducing Markovnikov’s rule: the formation of a more stable R+ is favored b/c it’s a lower energy process

Alkene additions proceed faster via a more stable R+ IM (kinetics)

Tri-substituted carbons are favored over mono-substituted carbons

X is added to the more substituted carbon

Always watch for stereochemistry! Enantiomers can be formed as products

Carbocation Rearrangements

Carbocation rearrangements will occur so the R+ is as stable as possible

That’s why the Markovnikov product won’t always be the major product

Rearrangements usually occur through hydride shifts, but alkyl shifts can also happen if that’s the only possible route

Remember: always check to see where the positive charge is at− if you can shift a hydrogen or methyl group over to make that carbon extra substituted, then it’s probably right

With the orbital alignment (aka alkyl shift), there’s a filled-empty orbital overlap, where the migrating bond is aligned with the empty 2p orbital

Ring Expansions

Some questions are gonna ask you to do ring expansions, so always think alkyl shifts (again, this is so we form the most stable R+)

NUMBER. YOUR. CARBONS. This will get messy

Note that even though the di-substituted carbon doesn’t change after the first arrow, the shape changes from cyclopentane to cyclohexane, so it’s thermodynamically more stable

Hydration

This follows Markovnikov’s rule− the OH group is always on the more substituted carbon of the alkene

Also this is pretty much a repeat of HX addition, but with some acid-base action

Pro-tip: your catalyst, H3O+, is always gonna be the electrophile, and your nucleophile is always gonna be the double bond, so START THERE!

There’s gotta be water after that first step (hydration, duh)

Your water is now a nucleophile, and it’s gonna start attacking the R+

Remember to follow through with any possible R+ rearrangements− we won’t need it here b/c the R+ is already tri-substituted

Your catalyst MUST be regenerated!! *insert acid-base reaction*

Side note: alkene dehydration is the reverse of hydration and is an E1 process

DON’T ADD H2O/H3O+ UNDER DEHYDRATION CONDITIONS

Instead, use a strong acid, like concentrated H2SO4

Oxymercuration-Demercuration

This is essentially an alkene “hydration” w/o the rearrangement part

We don’t have rearrangement b/c the mercurinium ion doesn’t have a carbon

When the mercurinium ion bridge breaks, the nucleophile (in the second example, water), attacks the MORE substituted carbon, whereas the HgOAc attacks onto the LESS substituted carbon

The OH and HgOAc add ANTI to each other, but then the H from BH4- changes orientation on the LESS substituted carbon (forming diastereomers)

Side note: as a variation, you can also use an alcohol (ROH) instead of H2O in the oxymercuration step

Hydroboration/ Oxidation

The double bond nucleophile attacks the empty orbital in BH3

The BH3 attaches onto the LESS substituted carbon, so the positive charge builds on the MORE substituted carbon

I like drawing the third H in BH3 as an extension of BH2, so I can visually see the hydride shift

The OH from the peroxide basically replaces the BH2

The specific steps with BH3 get messy, so I was taught a revised method− basically, a concerted addition of BH3 w/ an internal H- transfer

There is regioselectivity in the sense that the partial positive charge follows Markovnikov’s rule

There is stereospecificity due to the syn (same side) addition of H and BH2 in the hydroboration product

Alkene Halogenation

Note that I2 doesn’t work here as a possible halogen

Markovnikov regioselectivity is present

There is ANTI stereospecificity, as in the two individual X’s from X2 attach themselves as opposite wedges and dashes

Alkene Halohydrin Formation

This is very similar to the previous alkene halogenation, except the second X in X2 doesn’t attach onto the final product

Rather, the nucleophile replaces the second X

Markovnikov regioselectivity is also present (this is SN1-like)

There is ANTI stereospecificity yet again (this is SN2-like)

And that’s it! Well, this is a good chunk of alkene reactions (and a pretty brief version of it). Regardless, I hope this is helpful! I hope to follow up with extra review mechanisms for additional alkene and alkyne reactions. Thanks for reading!!

productivepls

For future