Tag: organic chemistry

Learning Organic Chemistry is Like Learning Another Language

Learning organic chemistry is like trying to work in a foreign country where if you don’t know the language, it is going to be very difficult to learn how to do your job.  You have just been transported to the mythical country of “ochemia”, a small island nation in the south Pacific, where your job is to write chemistry reactions. 

Frequently, in a chemistry lecture, professors start tossing out organic chemistry terms far too quickly.  Because students aren’t fluent in “ochemia” yet, they need to translate each word in their head to understand what the instructor has just said.  By the time this mentally translation is done, the student has just missed the next sentence and has lost half of the lecture.  Our goal is to get as fluent as we can in the language of chemistry as quickly as we can.  Here are some terms it will be helpful to memorize so that you don’t have to do a mental translation when you hear them:

Meth = 1

Eth= 2

Prop = 3

But = 4

Pent = 5

Hex = 6

 Hept = 7

Oct = 8

Non = 9

Dec = 10

Electrophile = wants electrons, has a positive or partial positive charge

Nucleophile = has electrons, has a negative or partial negative charge

Halogen = F, Cl, Br, I

Aprotic solvents = do not contain OH or NH bonds

Protic solvents = contain OH or NH bonds

Lewis Acid = electron acceptor

Lewis Base = electron donor

Carbonyl group =  (C=O)

Cis = same side of a double bond or ring

Trans = opposite sides of a double bond or ring

 

 

A comprehensive organic chemistry glossary can be found at: http://www.chemhelper.com/glossary.html

 

As always, for more help in organic chemistry, please go to Organic Chemistry

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Organic Chemistry Study Tips: Study In Packs

This reminds me of my favorite video on YouTube (http://www.youtube.com/watch?v=LU8DDYz68kM).  You are a pack of wildebeest, just chilling out by the water, trying to score a good grade in organic chemistry.  But you are being hunted by pride of hungry lions (your professors) who would like nothing better to make a quick snack of the weakest one of you.   After crouching in the brush, they suddenly pounce (pop quiz) and grab a hold of the smallest one of you (the student with the hardest course load). 

 

Two things can happen at this point:  Either the rest of the pack of wildebeest will cut their losses and try to save themselves or they can go back and heroically battle the lions to save their fallen colleague.  I am not going to ruin the video if you have not already viewed it, but I think you already know what happens. 

 

Studying in packs presents a number of benefits other than just altruistically helping a lesser student:

1)      Studies have shown over and over that studying in groups directly leads to higher grades of all involved.

2)      Studying in groups is generally more enjoyable for people, which leads to more time spent on the subject.

3)      If you are weaker in one area of the course, you have the opportunity to have a peer explain it to you.  Many students are more likely to understand a peer’s explanation over a stuffy professor’s.

4)      If you are stronger in one area of the course, you will strengthen your overall understanding of chemistry by teaching it to someone else.

 

Of course, when you are choosing study partners on the Serengeti, you need to be very careful to stay away from the jackals.  These are the students that are more parasite than human and will just leach off of your talents.  They are more succubus than man and will not help you much.   We suggest finding study partners that are interested in a good grade and are willing to put in the time necessary to achieve a good grade in the course.      

For more information and organic chemistry help, please go to organic chemistry

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Organic Chemistry Help: Resonance

Hi Everybody–Resonance is one of those issues that you will have to deal with for both semester I & II organic chemistry.  It is much better to have a solid understanding of it now, rather than have to worry about it later.  The basic goal of resonance structures is to show that molecules can move electrons and charges onto different atoms on the molecule.  This makes the molecule generally more stable because the charge is now delocalized and not “forced” on an atom that does not want it.

 

Below are some handy rules of resonance.  If you learn these and think about them when tackling different resonance problems, you will be able to handle whatever is thrown at you.

 

1) Know each atom’s “natural state”.  You need to recognize what each atom generally looks like, in an uncharged state.  This will help you to construct the Lewis Dot structure on which you will base your resonance structures.  In most uncharged cases:

       – C has four bonds and no lone pairs

       – N has three bonds and one lone pair

       – Halogens (F, Cl, Br, I) have one bond and three lone pairs. 

       – O has two bonds and two lone pairs

       – H has one bond and no lone pairs

       – With the exception of H, everyone in group I & group II are only counterions (+1 or +2 and not involved in resonance).

Remember that halogens and hydrogens are always terminal, meaning that are at the end of the molecule and only have one bond, and therefore, they will not participate in resonance.

2) Atom positions will not change.  Once you have determined that an atom is bonded to another atom, that will not change in a resonance structure.  If they do change, it is no longer a resonance strucutre, but is now a constitutional isomer.

 

3) Check the structure you have created to make sure that it follows the octet rule.  This will become much easier once you have a better handle on the “natural state” of atoms.

 

4) When two or more resonance structures can be drawn, the one with the fewest total charges is the most stable.  In the example below, A is more stable than B.

 

 

5) When two or more resonance structures can be drawn, the more stable has the negative charge on the more electronegative atom.  In the example below, A is more stable than B.

 

6) In the end, each resonance structure should have the same overall charge and total number of electrons (bonds + lone pairs) as when you started.

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Organic Chemistry Help: More on Electrophilic Aromatic Substitution

Hey Everybody, here is a good trick to keep in your back pocket if you run across an EAS question where you have something in the ortho position, but not the para.

Here is a good trick to do it: First, bromonate your benzene ring under standard condition, then sulfonate using SO3/H2SO4.  This will make the para bromo sulfonate.  Now the next substituent, our chlorine, will be directed ortho to the bromine.  We now have a trisubstituted arene ring and can remove the sulfonate unsing acidic water.  This gives us a nice route to the ortho di-halide without having to justify why we got a mixture of the ortho and para products. 

 

For more information on this, please go to organic chemistry

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Organic Chemistry Help: Retrosynthesis on an enolate

Hi everybody, one of the questions I hear alot is about enolate product.  How do you do the retrosynthetic analysis on one?  How do you even know it came from an enolate reaction?  Here is an example to look at:

As you can see here, a possible enolate product is an α,β-unsaturated ketone.  When you see one of these types of ketones, disconnect first at the double bond and “insert” an oxygen atom, as shown above.  Now, it becomes more evident which two carbonyls were participants in the original reaction.
Remember that in most cases, an α,β-unsaturated ketone can be derived from an enolate reaction.
Hopefully this was somewhat helpful.  For more information on this and other topics, please visit organic chemistry.
Good luck and happy reacting.

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Organic Chemistry Site of the Week–Online Flashcards

So, most of you are probably just starting your organic chemistry II lectures rights now.  It might be a little early to introduce this site, but it is definitlely one of my favs.  It is run by THE (emphasis added) Ohio State University, and consists of organic chemistry flash cards.   I have gone thru them all and they are a great resource.  Check it out, it will be a big help for all undergrad o-chem student.

Good luck and happy reacting.

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Starting Organic Chemistry II

Hey Everybody, welcome to semester II.  Hopefully everybody survived the first semester and are ready to clobber “Organic Chemistry Part Deux”.

 One of the questions I get asked alot are about the differences between Semester I and II.  In semester I, you are building the foundation of your house so you need to learn things like nomenclature, stereochemistry, and functional groups.  Most people do some reactions (SN1, SN2, E1, E2) but it is very limited. 

 Semester II will focus on learning reactions.  This is a very good thing for the memorizers out there.  In addition to the simple reactions, you will also have multi-step syntheses and retrosyntheses (working backwards) to complete.  This becomes a big stumbling point for many people, because putting it all together can be difficult.  In future post, I will go over the best way to tackle a multistep problem, but that won’t be until middle semester. 

So until the next post, good luck and happy reacting.

For more information on this, please visit organic chemistry help

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