Sciencemadness Discussion Board - Very First Step into Organic Chemistry

Very First Step into Organic Chemistry

aga - 28-3-2015 at 13:30

Can anyone suggest a practical experiment (preferably with a reference) that would offer a Way Into OC ?

Personally i find if baffling, and cannot see a way in.

Yes, i've done some OC, and understand not one iota of it.

Today some linseed oil decided to puff smoke at me, and i really really would like to have some handle on the Why.

To be fair, the oil had been treated badly with SCl₂ and a bit of ammonia, so it had just cause.

Loptr - 28-3-2015 at 14:46

One of the first organic experiment I attempted at home was a Fisher esterification of ethanol and acetic acid to produce ethyl acetate.

Its a common example for the Fischer esterification.

Cheap and easy to handle reagents.

[Edited on 28-3-2015 by Loptr]

Etaoin Shrdlu - 28-3-2015 at 14:49

Dehydration of a secondary or tertiary alcohol to make alkenes, that's pretty simple, and easy to see you've succeeded because the products distill at a much lower temperature than the alcohol.

http://www.nvcc.edu/alexandria/stb/chm/245/45_dehydration.pd...

[Edited on 3-28-2015 by Etaoin Shrdlu]

Molecular Manipulations - 28-3-2015 at 14:59

The first and most important step is to learn organic nomenclature, without this every IUPAC name, every chemical structure and every functional group will be a complete mystery. It's super easy and logical.
As for experiments, making an ester is fun. All you need is an alcohol and sulfuric acid. Nitrations are fun and yield a product that has energetic properties.

Just curious, how many of you recognize this off the bat?

Loptr - 28-3-2015 at 15:20

Quote: Originally posted by Molecular Manipulations

The first and most important step is to learn organic nomenclature, without this every IUPAC name, every chemical structure and every functional group will be a complete mystery. It's super easy and logical.
As for experiments, making an ester is fun. All you need is an alcohol and sulfuric acid. Nitrations are fun and yield a product that has energetic properties.

Just curious, how many of you recognize this off the bat?

Hell no, but please explain. I am still a novice with nomenclature.

Etaoin Shrdlu - 28-3-2015 at 15:21

Not going to show stereoisomerism, MM?

[Edited on 3-28-2015 by Etaoin Shrdlu]

Molecular Manipulations - 28-3-2015 at 15:33

What for that molecule? Stereoisomers are isomeric molecules that have the same molecular formula and sequence of bonded atoms (constitution), but that differ only in the three-dimensional orientations of their atoms in space. - Wikipedia.
It would take up way too much space just to quote a guide to nomenclature, it's not complicated, but there's a lot of definitions to memorize. Here's a link to a guide http://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/nome...
That's a rather well known molecule, at least around here

[Edited on 28-3-2015 by Molecular Manipulations]

Lambda-Eyde - 28-3-2015 at 15:40

Quote: Originally posted by Molecular Manipulations

Just curious, how many of you recognize this off the bat?

You don't think there are any stoners on the forum?

blogfast25 - 28-3-2015 at 15:42

aga:

Look at that chemistry book you bought. It has examples of most basic OC reactions and mechanisms. In many cases, like the on ES linked to, you'll find classroom experiments completely laid out for you.

I'd certainly recommend Fisher esterifications. Lovely smells if you make the right ones, easy to do and need basic work up techniques that are useful later on.

Etaoin Shrdlu - 28-3-2015 at 15:42

Quote: Originally posted by Molecular Manipulations

What for that molecule?

The "one everyone thinks of" is a specific stereoisomer. It was a joke. xP

[Edited on 3-28-2015 by Etaoin Shrdlu]

Loptr - 28-3-2015 at 15:52

Quote: Originally posted by Lambda-Eyde

Quote: Originally posted by Molecular Manipulations

Just curious, how many of you recognize this off the bat?

You don't think there are any stoners on the forum?

Oh, I get it now.

Sorry, I dont, as it goes with the job... Not to mention I have too many distractions in life, and dont need another.

aga - 28-3-2015 at 16:00

DOH !

You mean i have to Work to understand it ?

This internet thing isn't living up to expectations.

morganbw - 28-3-2015 at 16:01

Quote: Originally posted by Molecular Manipulations

I have some/much to learn. Your advise is dead on. It lays the foundation that is required to understand anything pertaining to organic chem.
Thank you sir, you reminded me of what I knew to be but have been lazy/sidetracked away from.

morganbw - 28-3-2015 at 16:26

Quote: Originally posted by aga

DOH !

You mean i have to Work to understand it ?

This internet thing isn't living up to expectations.

I am not there yet, but I am thinking that it is not really that much work.
Just a different challenge which if not taken will keep me behind where I want to be.

j_sum1 - 28-3-2015 at 17:25

I think I am in the same position as you aga. I know nearly no OC.

I have done esterifications, oxidation of alcohols and halogenation of unsaturated hydrocarbons.
I know about simple nomenclature, some of the more basic functional groups, isomerism, polymers and some general principles for correlating structural formula with physical properties and (some) chemical properties.
Get me into aromatics or start talking about alpha carbons or ask me to choose a catalyst or break a C-C bond and the wheels fall off.
I am going to make oil of wintergreen from aspirin with my class in a few weeks -- and that is mostly to get some experience with some new techniques. I am going to follow MrHomeScientist's youtube clip. It looks straightforward and fun.

And since someone else posted it recently, here is an elementary road map for the field. It might be useful.
http://www.compoundchem.com/infographics/#orgchem

Chemosynthesis - 28-3-2015 at 18:27

Have you looked for organic chemistry lab books? Some are available online for various college courses, and have experiments one can perform at home with mechanisms and theory, designed to be learned alongside textbook readings.

Esterification can be fun and rewarding.

Darkstar - 28-3-2015 at 22:05

Like others have said, learning nomenclature, stereochemistry, and how to interpret skeletal structures and functional groups is a must. Being able to follow the flow of electrons (electron pushing) in a mechanism is necessary, too. Honestly, in addition to those things, I'd also start by learning about nucleophiles and electrophiles, specifically what they are and how to differentiate between them. Being able to correctly identify the nucleophile(s) and electrophile(s) in a reaction may very well be the single most important step in actually understanding it.

Start with some basic substitution and elimination reactions first. Try to stick to the more simple reactions of each type until it starts making sense conceptually, then slowly progress to more and more complex ones. For example, with the nucleophilic substitutions, start with very simple S_N1 and S_N2 reactions first. Once you start getting the hang of it, you can then move on to slightly more complex kinds of substitution, such as intramolecular substitution (ring closure) and those that involve an intimate ion pair (S_Ni).

For the time being, focus mostly on simple reactions whose mechanisms are known and have been studied for a long time. Forget about trying to make sense of reactions with mechanisms that aren't very well understood, for instance a lot of dissolving metal reductions and various other one-electron reductions involving free radicals and single-electron transfer.

deltaH - 28-3-2015 at 22:06

There a four classical reaction classes in organic chemistry, [1]addition, [2]substitution, [3]ellimination and [4]radical reactions, each have a few further subsets. After learning the basics about how to name and draw organic compounds, you can work your way through the theory of each of those reaction types and then try your hand at performing a reaction that is representative of each. That would be an excellent start.

aga - 29-3-2015 at 01:59

Thanks for the pointers.

Making ethyl acetate looks do-able, and has some indicator of success (smell) so i'll give that a go.

blogfast25 - 29-3-2015 at 06:47

Quote: Originally posted by aga

Thanks for the pointers.

Making ethyl acetate looks do-able, and has some indicator of success (smell) so i'll give that a go.

Methyl salicylate, very simple version:

https://www.youtube.com/watch?v=Nu2Excsv4zE

Salicylic acid = aspirin, so very OTC.

Also easy and lovely smelling: methyl benzoate. And if you have sodium benzoate then getting benzoic acid from it is a doddle.

[Edited on 29-3-2015 by blogfast25]

CuReUS - 29-3-2015 at 08:21

Quote: Originally posted by Lambda-Eyde

Quote: Originally posted by Molecular Manipulations

Just curious, how many of you recognize this off the bat?

You don't think there are any stoners on the forum?

that long n-pentyl side chain on the aromatic ring makes it look like a cannabinol derivative

[Edited on 29-3-2015 by CuReUS]

DJF90 - 29-3-2015 at 09:35

Quote: Originally posted by CuReUS

Quote: Originally posted by Lambda-Eyde

Quote: Originally posted by Molecular Manipulations

Just curious, how many of you recognize this off the bat?

You don't think there are any stoners on the forum?

that long n-pentyl side chain on the aromatic ring makes it look like a cannabinol derivative

[Edited on 29-3-2015 by CuReUS]

It is indeed (+/-)-delta-9-tetrahydrocannabinol. I made a few hundred grams of an ("inactive") analogue under Home Office license during previous employment. I wouldn't recommend it as a first attempt at organic synthesis though.

[Edited on 29-3-2015 by DJF90]

brubei - 29-3-2015 at 10:13

Performing organic synthesis is pleasant when you can identify your product apparition and deseappearition. Learning TLC monitoring is a good way to do that.

then TLC can be used for simple analytic technique with almost every thing you can find. Searching for alcaloid, protein, oils, etc in food, flower ...

here is a good textbook, you can learn to recognize the organic function in a molecule, maybe how they react.
http://www.clubdeccm.com/PDF/Dyeing_Reagents_TLC.pdf

[Edited on 29-3-2015 by brubei]

BromicAcid - 29-3-2015 at 12:53

I did inorganic synthesis for years in my back yard and it was strange when I had to actually do an organic reaction. At the time I thought I was going to grow up and become an inorganic chemist (college taught me that was a lot different than I would have hoped) so I really didn't want to even try orgo. I remember my first synthesis clearly, nitrobenzene. Easy to conduct, easy to purify, excellent (headache-inducing) smell. The motivation was purely to get a solvent to carry out the electrolysis of NaCl/AlCl3 mixture. Out of hundreds of home chemistry experiments I probably only performed a dozen or so organic transformations. Sure, a nitration can seem like a reaction for all the energetics people out there but the standard organic chemist does have reason to fish the reaction out of their repertoire from time to time. Yields are good, I would certainly recommend it to others as a first experiment, plus if you don't have benzene you get to make that first, another exciting complication.

aga - 29-3-2015 at 13:35

Just finished having a go at Ethyl Acetate.

Had to make Acetic Anhydride first, so it took a while.

( 30ml Ethanol close to anhydrous, 30ml Acetic Anhydride, 6ml 98% H2SO4, reflux 30 mins)

Must have worked as the smell is now that of NVR instead of vinegar, however it won't separate from the 'neutralised' reaction mixture.

Some questions :-

If you're going to reflux with heating, is there any point cooling the mixture as you add the acid ?

Is it necessary to neutralise the acid after the reaction ?

blogfast25 - 29-3-2015 at 14:58

Quote: Originally posted by aga

Had to make Acetic Anhydride first, so it took a while.

( 30ml Ethanol close to anhydrous, 30ml Acetic Anhydride, 6ml 98% H2SO4, reflux 30 mins)

Must have worked as the smell is now that of NVR instead of vinegar, however it won't separate from the 'neutralised' reaction mixture.

Some questions :-

If you're going to reflux with heating, is there any point cooling the mixture as you add the acid ?

Is it necessary to neutralise the acid after the reaction ?

You meant anhydrous acetic acid, aka glacial acetic acid, 'acetic anhydride' is something quite different:

http://en.wikipedia.org/wiki/Acetic_anhydride

If the ester didn't separate out that's most likely because there was still too much water in your reagents. The catalyst is concentrated sulphuric acid: dilute it too much and it won't work.

google for a decent prep of ethyl acetate, there are oodles of them.

Normally you separate the reaction water from the ester, then neutralise any remaining acid in the ester and distil it for purity.

Texium - 29-3-2015 at 19:08

I would highly recommend methyl salicylate rather than ethyl acetate as a first esterification, because unless you have pure glacial acetic acid or acetic anhydride, it's unlikely that you will have much success with ethyl acetate. With esterifications, you need to do whatever you can do to keep water out of the system. Otherwise, you'll have virtually no yield. Methyl salicylate is much easier. You can make salicylic acid from aspirin (acetylsalicylic acid) by hydrolyzing it using hydrochloric acid, and then reflux that with methanol and a bit of sulfuric acid for a few hours. If you don't have access to methanol, you could try making ethyl salicylate. It's supposed to work exactly the same, although it didn't for me, so I can't personally vouch for it.

Here's a couple of useful links from our very own wiki:
Methyl Salicylate
Synthesis of Salicylic Acid

Edit- I also just want to say, that I only recently started getting into organic chemistry myself, but I am really enjoying it, and think that I will shift my main focus towards it.

[Edited on 3-30-2015 by zts16]

Darkstar - 29-3-2015 at 23:40

Quote: Originally posted by zts16

I also just want to say, that I only recently started getting into organic chemistry myself, but I am really enjoying it, and think that I will shift my main focus towards it.

*evil grin*

Yes, yes. Excellent. You, j_sum, Cou, aga...all of you just come on over to the dark side. That's right. That's right...

kavu - 29-3-2015 at 23:52

Quote: Originally posted by aga

Some questions :-

If you're going to reflux with heating, is there any point cooling the mixture as you add the acid ?

Is it necessary to neutralise the acid after the reaction ?

The point of cooling in the first place is to prevent an overrun reaction. Sulfuric acid can readily protonate a variety of species in such a reaction mixture, releasing a lot of heat. There is also the possibility of conc. sulfuric acid forming a dense lower layer at the bottom of the flask leading to all sorts of nasty side reactions including dehydration reactions, so stirring is in place here.

Neutralization of the acid (so-called quench) is needed, the reaction mixture will contain water from the esterification (check the mechanism). If left like this it will undergo an acid catalyzed ester hydrolysis and eventually reach an equilibrium where your product is partially hydrolyzed back to starting materials. Such an equilibrium exists in the reaction as well, but excess of alcohol is usually used to drive it towards completion. Upon neutralization the reaction effectively stops as the catalytic proton source is depleted.

Most every organic synthetic procedure calls for a quench of some type. This is typically a neutralization/acidification/hydrolysis procedure to kill one or few of the reacting species.

As for starting with organic chemistry I can highly recommend the famous NotVoodoo-site (experimental shenanigans) as well as the very clearly written theoretical resource MasterOrganicChemistry.

[Edited on 30-3-2015 by kavu]

aga - 30-3-2015 at 00:21

Wow !

Thanks to all for the interesting and useful info/links.

The 'overrun' sounds perfectly sensible, and i think can see the point now : if it gets too hot Other evil darkside reactions happen.

Once it's reacted to as much of the target product the catalyst needs removing to prevent further Other darkside reactions happening.

The excess ethanol to push the equilibrium to the side you desire is also making some sense, although i'm unclear as to why it'd be the ethanol in excess rather than the glacial acetic acid.

I definitely had too much water in the mix as the acid didn't seem to want to be neutralised, so i kept adding and adding ...

So, in a nutshell, it's all a Balance, in that there isn't 1 reaction at all, there are many.

What you Sith Masters are doing is carefully balancing reaction conditions to achieve as high a veild of the target compound as possible, at as high a purity as possible.

Darkstar - 30-3-2015 at 00:39

Quote: Originally posted by aga

The excess ethanol to push the equilibrium to the side you desire is also making some sense, although i'm unclear as to why it'd be the ethanol in excess rather than the glacial acetic acid.

Excess GAA would indeed drive the equilibrium to the right as well. Since the reaction is reversible, the ethanol and acetic acid are in equilibrium with ethyl acetate and water:

EtOH + AcOH ⇌ EtOAc + H₂O

An excess of something on the left side shifts the equilibrium over to the right. An excess of something on the right side shifts it over to the left. This is also why you want as little water present in the reaction mixture as possible.

morganbw - 30-3-2015 at 00:41

Quote: Originally posted by aga

Thanks for the pointers.

Making ethyl acetate looks do-able, and has some indicator of success (smell) so i'll give that a go.

Here is a file which I snatched from the web. It gives a fairly nice overview
and does go into the purification.

Attachment: A2 Expt13.5(3) The Synthesis of Ethyl Ethanoate Teacher guide.doc (42kB)
This file has been downloaded 27041 times

kavu - 30-3-2015 at 01:10

Quote: Originally posted by aga

What you Sith Masters are doing is carefully balancing reaction conditions to achieve as high a veild of the target compound as possible, at as high a purity as possible.

A good starting point is usually to refer to the reaction mechanism, a stepwise depiction of how the reaction (likely) will take place. If you notice key intermediates and points where side reactions can take place you can adjust temperature/solvent/reagents and so on accordingly. Also checking the literature gives you a good picture of how a reaction is typically carried out.

Key to a successful synthesis is monitoring. You need to be constantly checking on the reaction: has the starting material been consumed, are there products forming, how many products, is the reaction clean and so on. Typically this is achieved using a combination of TLC, 1H NMR and GC/LC-MS.

Optimizing for high yields calls for numerous experiments carefully changing reaction parameters one at a time. This will paint a parameter landscape of how the reaction selectivity/yield behaves allowing to pinpoint the highest yielding combination. Typically the parameter space is too huge to cover exhaustively so compromises are in place.

aga - 30-3-2015 at 01:21

@morganbw: Thanks ! In light of 'pushing the equation to the right' info, that paper makes more sense than the other process i tried.

So by distilling off the EtOAc as it forms, and adding more reagents, the equilibrium is biased over towards the right hand side (more EtOAc). I think i just learned something !

@kavu: I'll seek out the reaction mechanism and see if i can make sense of it.
TLC is do-able, but i can't remember seeing any NMR or GC/LC-MS equipment in my shed ...

Would it be the case that OC can be so immensely complex that the Only way to really know what the Product(s) are is to analyse them using seriously high-tech kit ?

Edit:

Just stumbled on this explanation of that particular mechanism:-
http://www.chemguide.co.uk/physical/catalysis/esterify.html

[Edited on 30-3-2015 by aga]

brubei - 30-3-2015 at 02:07

Quote: Originally posted by aga

@morganbw: Thanks ! In light of 'pushing the equation to the right' info, that paper makes more sense than the other process i tried.

So by distilling off the EtOAc as it forms, and adding more reagents, the equilibrium is biased over towards the right hand side (more EtOAc). I think i just learned something !

You cant distil AcOEt while your reaction isnt finished, because the boilling point of AcOEt and EtOH are too close 77°C ans 75°C

Catching the water as far as it is produced by adding dessicant (like moleculare sieve) is the best way do displace the equilibrium.

Quote: Originally posted by aga

Would it be the case that OC can be so immensely complex that the Only way to really know what the Product(s) are is to analyse them using seriously high-tech kit ?
[Edited on 30-3-2015 by aga]

TLC is not so high tech
OC is not as simplex as you can read on paper.

Doing a reaction is often followed by secondary product and you have to deal with the unreacted products. The purity of the compound that you aim to produce is far to be guaranteed so you have to check it.

Checking the content of your mixture is also the way to learn how to handle chemistry. It allow you to see the influence of your experiments when you decide to take initiatives by changing or creating your protocol.

[Edited on 30-3-2015 by brubei]

Loptr - 30-3-2015 at 06:31

Quote: Originally posted by Darkstar

Quote: Originally posted by zts16

I also just want to say, that I only recently started getting into organic chemistry myself, but I am really enjoying it, and think that I will shift my main focus towards it.

*evil grin*

Yes, yes. Excellent. You, j_sum, Cou, aga...all of you just come on over to the dark side. That's right. That's right...

I have been rereading through the inorganic sections of my college chemistry books in hopes of gleaning more about potential catalysts, etc., for the time I intend to spend in amateur organic chemistry.

Inorganic just bores me for some reason--I tend to be attracted to complexity for some reason. Yes, I know inorganic chemistry is what we first learn to gain some fundamentals in the various theories and techniques, but are there books out there that start from zero and go from there while providing a focus on Organic Chemistry? The books I have been reading tend to stay on the inorganic side of things.

kavu - 30-3-2015 at 23:35

Quote: Originally posted by Loptr

Yes, I know inorganic chemistry is what we first learn to gain some fundamentals in the various theories and techniques, but are there books out there that start from zero and go from there while providing a focus on Organic Chemistry? The books I have been reading tend to stay on the inorganic side of things.

I can highly recommend Organic Chemistry by Clayden Jonathan, Greeves Nick, Warren Stuart and Wothers Peter. This book, widely used in universities all around the world, starts from molecular orbital theory (effectively "zero") and relates that to organic reactivity.

[Edited on 31-3-2015 by kavu]

aga - 3-4-2015 at 11:11

Inorganic, Organic - it's all great.

The basic thing i get from exploring OC is that nobody really knows what's going on (compared to IOC) which is wonderful.

Temperatures are also generally lower, which is helpful.

Loptr - 3-4-2015 at 11:19

You can have a very good idea, but it starts to get math and computationally intensive.

When I go back for my masters in the next year or so, I am toying around with the idea of computational chemistry. I have the computer science and math background (rusty), but it should be fun.

Not that I would actually use it in my job...

[Edited on 3-4-2015 by Loptr]