For those unfamiliar with this type of question: Sometimes you are only given the final product and asked to list the reactions necessary to synthesize given some parameters start only with a compound that has 5 carbons or less, only use alcohol, etc. My plan is to use the SMILE format for reading molecules since I can manipulate it as I would a stringthen define functions for each reaction, finally I'll need a database of chemical species which the program can randomly select species from for the inital and final species in the problem. The program then selects a random species from the database, applies a bunch of reactions to itspecified by the user then displays the final product.
Nomenclature and preparation of epoxides Video transcript One way to make ethers is to use the Williamson ether synthesis, which is where you start with an alcohol, and you add a strong base to deprotonate the alcohol. Once you deprotonate the alcohol, you add an alkyl halide, and primary alkyl halides work the best.
We'll talk Simple retrosynthesis problems why in a minute. And what happens is you end up putting the R prime group from your alkyl halide on to what used to be your alcohol to form your ether like that. So let's look at the mechanism for the Williamson ether synthesis, where you start with your alcohol.
We know that alcohols can function as weak acids. So if you react an alcohol with a strong base, something like sodium hydride, we know that the hydride portion of the molecule is going to function as a strong base.
This lone pair of electrons is going to take that proton, which is going to kick these electrons off onto the oxygen. So if we're drawing the product of that acid-based reaction, we now have an oxygen with three lone pairs of electrons around it, giving it a negative 1 formal charge.
And we call that an alkoxide anion, which would interact with the positively charged sodium ion floating around. So there's some electrostatic or ionic interaction between those opposite charges.
And here's where you introduce your alkyl halide. So if we draw our alkyl halide, it would look like this. And we know that there's an electronegativity difference between our halogen and our carbon, where our halogen is going to be partially negative, and our carbon is going to be partially positive.
Partially positive carbon means that that carbon wants electrons. It's going to function as an electrophile in the next step of the mechanism. And a lone pair of electrons in the oxygen is going to function as a nucleophile. So opposite charges attract.
A lone pair of electrons on our nucleophile are going to attack our electrophile, our carbon. At the same time, the electrons in the bond between the carbon the halogen are going to kick off onto the halogen like that. So this is an SN2-type mechanism, which is why a primary alkyl halide will work the best, because that has the decreased steric hindrance compared to other alkyl halides.
So what will happen is, after nucleophilic attack, we're going to attach our oxygen to our carbon like that, and we form our ether. So if we wanted to, we could just rewrite our ether like this to show it as we added on an R prime group like that.
Let's look at an example of the Williamson ether synthesis. So if I start with a molecule over here on the left, and it's kind of an interesting-looking molecule.
And so beta-naphthol has two rings together like this, and then there's an OH coming off of one of the rings, like that. And in the first part, we're going to add potassium hydroxide as our base. Now, potassium hydroxide is not as strong of a base as sodium hydride is, but in this case, it's OK to use a little bit weaker base.
So the lone pair of electrons on the hydroxide are going to take that proton, leaving these electrons behind on the oxygen. So when we draw the conjugate base to beta-naphthol-- and we can go ahead and show that-- we're going to take off that proton, which is going to leave that oxygen there with three lone pairs of electrons, giving it a negative 1 formal charge.
So this is our alkoxide anion. And this alkoxide anion is resonance stabilized. So a resonance-stabilized conjugate base stabilizes the conjugate base, which makes beta-naphthol a little bit better acid than other alcohols that we will talk about.A unique approach to teaching and learning problem-solving and critical-thinking skills in the context of retrosynthetic analysis is described.
In this approach, introductory organic chemistry students, who typically see only simple organic structures, undertook partial retrosynthetic analyses of real and complex synthetic targets.
Multiple reasonable answers were possible for the questions. Organic synthesis of small molecules is the most challenging and intriguing area of research in the chemical science related disciplines. In the early 20 th century, the field of synthetic organic chemistry, while established in many respects, was to continue a sharp path of progress and advancement for over a century to reach the level of power and sophistication that it possesses today.
Problem Set 8 Solutions April 22, 1.
Draw a retrosynthetic pathway to synthesize penicillin (shown below) from simple starting materials. Chem D. J. Wardrop [email protected] Although this method may work for simple synthetic problems that require only one or two steps, Once the retrosynthesis is complete, the forward reactions can be written including all .
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April. saturday. April 22nd. 8pm Eastern, 7pm Central, 5pm Pacific. Presented by. leah fisch. This video also provides retrosynthesis problems and examples of the aldol condensation reaction where you have to find the aldehydes and ketones that combine to form the alpha beta unsaturated ketone or michael acceptor.