Is it E1, E2, SN1, or SN2??

 

 

 

This is such a common question, not only for students but on exams too.  How the heck do you tell the difference between an SN1, SN2, E1, E2 reaction?  Check out the chart below to start.

 

SN1, SN2, E1, E2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The factors that will decide:

1) Do you have a strong nucleophile?  If you do, it would favor an SN2 reaction.  If it mediocre, it will favor an SN1 reaction.

2) Does your nucleophile double as a base? If yes, it is going to favor elimination (E1/E2) over substitution (SN1/SN2).

3) How good is your leaving group?  If it is awesome, it is more likely to be a carbocation intermediate, ie E1 or SN1 reaction.  If the leaving group is only OK, that means it has to be forced off and is more likely to be a concerted reaction mechanism like SN2 or E2.

4) What is your solvent? Polar protic solvents will stabilize a carbocation better, therefore promote an E1 or SN1 reaction.  Polar aprotic solvents favor SN2 and E2.

5) What kind of substrate do you have?  If your starting material is a tertiary substrate, you are definitely E1 or SN1.  If it is a primary substrate,  you are definitely SN2 or E2. If it is a secondary substrate, it could go any one of the ways.

 

Let’s look at an example.

SN1 reaction

 

 

 

 

 

This is an easier example, but let’s start with it.  Here is the most important thing to see: The product has OTf substituted, NOT eliminated.  Just by looking at the product, we know it has to be an SN1 or SN2 reaction NOT an E1 or E2 reaction.  Therefore, when we look at the different factors below, we are going to ignore E1 and E2.

1) Nucleophile: Cl is good but not great. Mediocre Nu = SN1

2) Basic: NaCl is not basic.  No base = SN1/SN2

3) Leaving group: OTf is a dynamite leaving group.  Awesome LG = SN1

4) Solvent: tBuOH is a polar protic solvent = SN1

5) Substrate: It’s tertiary at the leaving group = SN1

All of the factors point to an SN1 reaction, therefore I feel comfortable saying it is an SN1 reaction.

 

How about this one:

an SN2 reaction

 

 

 

 

This is still clearly a substitution, but it’s on a secondary substrate, so it could go either SN1 or SN2.  Here are the factors:

1) Nucleophile: CN is a great nucleophile.  Great Nu = SN2

2) Basic: NaCN is not basic.  No base = SN1/SN2, but we already knew that.

3) Leaving group: Cl is a decent leaving group. Decent LG = SN2

4) Solvent: acetone is a polar aprotic solvent = SN2

5) Substrate: It’s secondary at the leaving group = SN1 OR SN2

Almost all of the factors point to an SN2 reaction, with the notable exception of the type of substrate.  I still feel comfortable saying it is an SN1 reaction.

 

What do you think?  Comment below and tell us all about it.

 

 

 

 

 

Large-Scale liquid manufacturing

I recently ran across eliquidwholesaleusa.com. I found the site really interesting, from a chemistry point of view. They are an insured wholesale e-liquid manufacture. They offer such services as custom private labels, wholesale supplier services, and an ISO-7 clean room for manufacture, which is coming soon. They are special for number of reasons. They have a lengthy history in the industry, all of their products are insured, they are dedicated to quality control, and they have some of the lowest cost in the industry.

I think they are especially good for the new upcoming business who wants to wholesale their products, but doesn’t really know where to start. Their customer service is pretty good, so they will be able to start you off on the right foot. Furthermore, they do private labeling, which is really cool for the start-up company that wants their own label and branding. You can explore the limitless possibilities by starting with your own manufacturing label using this site.

Their production facility is really unmatched in this space. They take it personally upon themselves to make the highest quality liquids, and customer satisfaction is their number one goal. They own a 10,000 square-foot facility allowing them to produce nearly 1,000,000 bottles a month. Everything is manufactured in a free and clean space to preclude contamination. They have the highest standards of manufacturing to make sure that they provide a safe and satisfactory product for their clients. Their industry knowledge is unmatched, they have competitive pricing, and a widely customizable product.

If you are interested in starting your own e-liquid private label or are just curious about the chemistry that goes along with a manufacturing facility like this, I suggest you check out their site. They are only a click away and you can pick up some pretty good information on industrial chemistry.

The top 7 organic chemistry sites you need to visit

Hi Chemists–

Organic chemistry is tough enough without having to search the whole web looking for more help.  So let us do the work for you. Here are our favorite sites to give you that edge in organic chemistry.  By the way, these are all free sites!

 

1) Japanese Spectral Database: On this site, you can type in almost any organic molecule (by mass, formula, or name) and will be able to view many of it spectra, including 1H NMR, 13C NMR, IR and mass spec.  Great resource, especially for the lab portion of the course.
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2) Mechanism Movies: This site has numerous animations of organic chemistry mechanisms, which is good because we think it is helpful to actually visualize where and how the molecules themselves move.  It is also nice to see transition states of reactions and get a feel for the size of the participating atoms and reactions sites.Slide6

3) Chemical Forums:  Got a question that you want to run by a few friends that you haven’t met yet?  This is the site.  Great (and pretty active) posting community where they will help you through a difficult problem or topic.  One word of caution–read the TOS before you go on.  The biggest thing is that they want you to have tried to figure it out a little yourself before posting on it.
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4) Organic Chemistry Test Bank: Shameless self-promotion alert!  We really do have the most comprehensive test bank on the internet.  It is all free (of course) and sorted by semester and difficulty of exam.  Most of the exams have answers too, which makes it a great place to sharpen your test taking skills.Slide2

5) The periodic table explained:  Ok, most of us don’t like to admit that there are elements out there other than C, H, N, O and the halogens….but they do exist.  What happens when you find yourself outside of the universe of atoms we are comfortable operating with?  Go look them up on this periodic table.  Click on any of the atoms and a pop-up will tell you all about it.  Really nice for those moments when you have wondered into the realm of inorganic chemistry.Slide3

6) Organic chemistry name reactions: A rose by any other name would smell as sweet”…true enough.  And yet if you don’t know what that name is, you might be totally in the dark.  That is where this site is helpful.  Should your professor toss out the name of an organic reaction, you can check this site to see what the heck that reaction is and what the mechanism is.  Big help.
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7) Molecule of the day blog: Two downsides here are that this is a little advanced and it has not been updated since 2011.  Two upsides are that it is kinda cool to look at some advanced stuff and figure out how the organic chemistry you know would work on this molecule AND (let’s be honest) undergraduate organic chemistry has not changed that much since 2011 so I think you’ll be fine.  Nice to look at some advanced chemistry to see how your knowledge can be used to understand something that has real life applicability.
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So there you have it.  I wouldn’t go to these sites everyday, but it is a good way to take a peed at some really helpful stuff and see chemistry from a viewpoint other than your professor’s…..and they’re all FREE!!

Students Reach Their Highest Levels at the Louisville Tutoring Agency

The Louisville Tutoring Agency (LTA), founded by Moshe Ohayon of Louisville, KY, is a premier tutoring and learning center, designed to give students the tools and educational foundation they need to succeed. Whether it’s mastering high school chemistry or getting higher ACT scores, LTA’s individualized approach helps students attain their academic goals with confidence.

What makes Louisville Tutoring Agency different is its approach. Most chain and franchise learning centers use the cookie-cutter method. Pre-written lesson plans and pre-made worksheets define their one-size-fits-all model. LTA realizes that each student is different, with different skill levels, talents, and tendencies. What works for one student may not work with another. The LTA approach works because it is designed to teach and support students
individually using their current school curriculum. Highly skilled educators and tutors work one-on-one with students, targeting specific issues and developing a plan to help them achieve their fullest academic potential.

LTA programs include private tutoring, after school homework help, summer enrichment classes, standardized test preparation, and college admissions counseling. Even the Futures ACT prep program, which is conducted in group sessions, relies on an individualized approach to produce results based on each student’s strengths and weaknesses. SAT, GRE, MCAT and LSAT prep tutoring is also available.

LTA tutors have exceptional academic credentials, ranging from advanced teaching certificates to professional degrees. Several even possess specialized backgrounds and experience tutoring special-needs students.

Founded by Moshe Ohayon of Louisville, KY in 2005, the Louisville Tutoring Agency offers parents and students a much-needed alternative when it comes to quality in academic achievement.

Even “Bad” Test Takers Can Improve Their ACT Scores

Millions of students take the ACT, but many are disappointed when they receive their scores. A low ACT score not only limits a student’s college options, but it can also reduce the student’s chances at scholarships. Why is it that many intelligent students do so poorly on the ACT?

Moshe Ohayon, founder of Bad Test Takers, set out to find out why smart kids have trouble getting high ACT scores. He discovered that students took the ACT as if it were like the tests they were used to taking at school. This tendency, Ohayon believes, causes students to go into the test totally unprepared. After years of study and experimentation, he devised a simple but revolutionary approach for taking the ACT, giving students the tools they need to tackle all four ACT sections in the most effective way.

He founded Bad Test Takers to teach students how to take advantage of what he and his team of expert tutors have learned about the ACT. An interactive online course takes students through each section of the test, teaching them how to abandon bad test-taking habits and learn new, sometimes seemingly counterintuitive ways to tackle the ACT strategically.

Ohayon and the Bad Test Takers team periodically retake the ACT to ensure the efficacy of their approach and to keep their years of experience finely honed. Based in Louisville, KY, the team also travels to schools across the country where they conduct workshops and seminars.

Steps of a Free Radical Reaction

This is one of the best depictions of a free radical reaction I have seen.   It shows what can go on in this reactions and how we get from starting material to desired final product.

Steps of a free radical reaction

 

Initiation = 1 neutral provides two radicals.  This is what starts the entire reaction.  This is also the only initiation step that can occur as CH4 is not going to participate in that type of reaction.

Propagation = 1 neutral + 1 radical provides a different neutral and a different radical.  In this reaction, the most likely propagation is chlorine abstracting a proton from methane to give HCl and the methyl radical.  The next step is where the methyl radical breaks up two Cl atoms.  What I really like about this depiction is that it shows that the Cl* from reaction 3 can be recycled back into step 2.  This means that the reaction is self-propagating.  This also means that IN THEORY you could have one initiation reaction, followed by a bunch of propagation, ending with one termination reaction.  Of course, in real life, for many reasons, this does not happen as there are lots of initiation reactions.

Termination = 2 radicals providing one neutral.  The part to remember here is that any two radicals can get together to terminate the reaction and form a neutral species.  Since we have 2 types of radicals in the reaction (Cl* and CH3*) , there are three combinations of potential termination steps.  Reaction 4 gives us back starting material, so it is fine.  Reaction 6 gives us product, so it is also fine.  Reaction 5 give us a byproduct, which strangely enough can replace methane in the propagation step and give us another by-product.

Think about this picture and figure out all of the side reactions that might occur to fowl up the reaction.  Then, (for you advanced students) think about what ways exist that you can minimize those side reactions.

Hope this was helpful to you all, and as always, happy reacting.