Organic Chemistry, "Form", Part 16 - Ketones & Nomenclature

Greetings,

This post explores ketones a bit further than the last post.  The "ketyl" functional group is a single carbon atom double bonded to an oxygen atom, with alkyl groups bonded to the ketyl carbon atom.

Ketones are very important compounds in several industries, which include coatings, painting, polymers, and pharmaceuticals.  One could say that a ketone compound is in a "fully oxidized" state.  The ketyl functional group will not readily accommodate the addition of another oxygen atom and there is no hydrogen atom to be lost.  Reduction of a ketone to an alcohol by the addition of hydrogen (Hydrogenation) can be readily performed with a wide array of reducing agents (such as sodium borohydride, NaBH4) or with the aid of a surface catalyst.

Ketones are named according to their carbon chain length and ketyl group position on the carbon chain when IUPAC rules are referenced.  Otherwise, a more common naming convention, using the names of alkyl groups attached to the ketyl group, is generally observed.  Ketone IUPAC names will tend to be used for scientific journal publications and compound-characterization electronic libraries, such as those used with FTIR (Fourier Transform Infrared Spectroscopy) analysis.  The following chart provides a few examples of structures and corresponding names for lower molecular weight ketones.

Note that IUPAC names for the two lightest ketones do not indicate the ketyl group position (Do you know why? See answer below.*)  Also the last two ketones listed are the only structural isomers consisting of a five carbon chain.

That's all for this post.  As always, thank you for reading!
 

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*"The Answer" - Propanone has only one possible location of the ketyl group, otherwise we would have an aldehyde!  Butanone may at first consist of a pair of structural isomers, but the ketyl group is always the second carbon of the chain, therefore no need to indicate its position!

Organic Chemistry, Form, Part 15 - Ketones, An Introduction

Greetings,

Another important class of organic compounds are the ketones.  Ketones are very similar to aldehydes: the only difference is that the "double-bond oxygen group" is never on the end carbon atom (otherwise you'd have an aldehyde).  Perhaps, the most common ketone is acetone; often used for cleaning and stripping solvents.

A ketone can be produced from a 2-degree alcohol (-OH group bonded to a carbon in turn bonded to two other carbon atoms).  We say the 2-degree alcohol is "oxidized" because hydrogen atoms are lost in the process.  More specifically, we call the process, dehydrogenation.  The following drawing shows the formation of 2-butanone from 2-butanol.

The red and blue dots are meant to indicate electrons which are lost along with a pair of hydrogen atoms.  The two hydrogen atoms, naturally, come together to form diatomic hydrogen gas.  The names provided for the alcohol and ketone are "systematic", but not official IUPAC.  Those names are buta-2-ol and buta-2-one.  IUPAC names are designed for easy determination of compound structures from the their names, but would be cumbersome to speak of in the lab, so chemists use names like those in the diagram.

That's all for now.  As always, thank you for reading!


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Organic Chemistry, Part 14, Form - Aldehydes - Second Part with a Video

Greetings,

This post provides a better look at the aldehyde structure.  A video showing a rotating 3-D Ball-and-Stick model has been prepared.


You may have noticed what appears to be a single covalent bond between the carbon and oxygen atoms.  That bond is actual double-covalent.

The molecular structure was drawn using "Avogadro": Individual frames were captured by taking frequent snapshots of the rotating model.  "Stop-and-Go" was used to freeze the frames.

"GIMP" was used to open the individual frames as layers in one file.  Further processing (Cropping and conversion to the ".gif" format) was also done using "GIMP".

Finally, "WeVideo" was used to combine tracks and publish as an mp4 file.

I hope you enjoyed the video!

Thank you for reading!

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Organic Chemistry, Form, Part 14 - Aldehydes - Structure and Nomenclature

Greetings,

This post focuses on Aldehydes; their structure and naming methods.

The Aldehyde is another type of organic compound formed from a slight modification of a hydrocarbon.  The aldehyde functional group is always built at the end carbon of a hydrocarbon.  Of course, the latter statement doesn't really apply to methane and ethane molecules, as they do not consist of a "middle" carbon atom.

Aldehydes are highly reactive compounds, often used to create a hydrocarbon "bridge" between molecules able to lose a hydrogen atom connected to a carbon.  An example of such a molecule is salicylic acid (an aromatic weak acid also consisting of a hydroxyl group).

The carbon of the aldehyde functional group (stated as, "C bond H, double-bond O ") is counted as part of the parent hydrocarbon for naming purposes.  Additionally. the aldehyde group is always at the end of the molecule, so its location does not need to be indicated.  For naming, we only need to indicate the number of carbons in the parent hydrocarbon and a way to note that we have an aldehyde functional group.  The following chart shows examples of molecular structures, Lewis formulas, and naming conventions.

One must be careful because the IUPAC name of an aldehyde closely resembles that of an alcohol.  Chemists working in a lab are more likely to refer to aldehydes using their stock names, as indicated above.

That's all for this post.  As always, thank you for reading!

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