Kemmy's Chemistry Blog

The name is Elliott Kemmy Parker. I'm a pre-med, biochemistry major at USD (get it? Kemmy? Like chem?).

[compoundchem]

August Kekulé was born #OTD in 1829  He’s famous for proposing the Kekulé structure of benzene, which he claimed was inspired by a dream of a snake seizing its own tail.

[labphoto]

Bromination with acetic acid, second part.

A concentrated bromine solution in acetic acid (approximately 30%) is added in a slow rate to another solution of an aromatic compound in acetic acid in the flask. The bromine reacts slowly, but it’s clearly visible that it has a much faint color compared to the added concentrated solution. 

As the reaction happens, the color will completely fade and if I am enough lucky, the product will precipitate from the solution, so only a filtration is needed as an isolation step. A great part of bromination in acetic acid is, that the produced hydrogen bromide stays in solution, because acetic acid dissolves it quite well, so almost no toxic fumes are produced from the reaction. However care should be taken, since bromine is highly toxic/corrosive, just as the produced HBr solution in acetic acid.

The mechanism of the bromination in case of Lewis acid catalyst (FeBr3): 

[labphoto]

Preparation of pyrrolidine carbonyl chloride on +100g scale. 

On the gifs you can see the beginning of the addition of the pyrrolidine to a solution containing a LOT (~200 g) of triphosgene. 

Triphosgene (bis(trichloromethyl) carbonate is a chemical compound that is used as a safer substitute for phosgene, because at room temperature it is a solid crystal, as opposed to phosgene which is a gas. It is a great reagent, since it could be easily handled and if it’s in a solution it decomposes to phosgene and reacts as I would use phosgene. 

On the gifs as the pyrrolidine contacts with the phosgene containing atmosphere it immediately reacts with it producing HCl gas what reacts with the pyrrolidine to form pyrrolidine x HCl which is a solid compounds and could be observed as fog in the glass.

Interesting fact: phosgene is HIGHLY TOXIC, so great care should be taken while working with it, always use PPE and a WELL working fume hood, but /do not try it out/ it has an odor in high dilution similar to freshly cut grass. 

[labphoto]

Copper catalyzed Ulmann coupling. It is ready when no more CO2 is generated from the reaction. It’s quite easily detected since, the question is, that is something bubbling in the gas bubbler (as seen on the gif) or no. If no, it’s done.

The blue color of the content of the flask is because of the copper salts used as a catalyst. At the end this pretty blue color fades and the whole reaction mixture turns into a red mass as seen on the following video:

For a bit more about Ulmann coupling:   

[labphoto]

The “Ullmann-type” Reactions include copper-catalyzed nucleophilic aromatic substitution between various nucleophiles (e.g. glycine) with aryl halides. On the video it is demonstrated that how does a reaction looks like when it is performed on a molar scale with over 100g of reactants using copper as a catalyst.

What happens in this reaction? This:

[labphoto]

Distilling a really toxic compound: ethyl fluoroacetate.

Fluoroacetic acid and related compounds are highly toxic. Any derivatives that contain fluoroacetate or degrades into fluoroacetic acid are highly toxic compounds with a LD50 as low as 0,25-2 mg/kg. This means that only a few drops of this chemical that can be seen flowing through the distillation apparatus is probably more than enough to cause serious problems. 

The unusually high toxicity of fluoroacetic acid and of other monofluorinated organic compounds that can be metabolized to fluoroacetate has stimulated much research into the mechanism of this toxicity. This acid inhibits the enzyme, aconitate hydratase, which normally catalyzes the dehydration of citric acid. As a result, citric acid accumulates in the organism and the energy-producing cycle is interrupted. The formation of fluoroacetyl CoA and the formation of fluorocitric acid is often referred as lethal synthesis. 

[skunkbear]

[skunkbear]

We turned this post into a video!

Tumblr Images: Charles D. Winters, Andrew Lambert Photography / Science Source, iStockphoto, Epic Fireworks, Softyx, Mark Schellhase, Walkerma, Firetwister, Rob Lavinsky, iRocks.com, Søren Wedel Nielsen

[npr]

Just in time for your holiday fireworks-viewing pleasure! -Ariel

[labphoto]

This fluorinated compound was obtained by the ammonolysis of an ester. Even through the compound was pure for most purposes, it was necessary to purify it before the next step by a recrystallization from chloroform.

It’s adorable to watch the needles growing from the clear solution in a perfect purity. The crystallization took more than half an hour so the video is significantly faster. Watch the video: https://www.youtube.com/watch?v=fMtlLPFTOTI

[cenchempics]

Bottled up

Chelsea Mueller and Michael Mattei ignited some scientific curiosity with this demonstration of volatility. The two graduate students at Northwestern University poured just 25 mL of isopropyl alcohol into an empty 5-gallon jug, covered the jug, and shook it up for about 30 seconds. The small amount of liquid spread over the large inner surface of the jug, coating it in a thin layer that evaporated quickly. As a result, flammable isopropyl alcohol vapors filled the jug. When the scientists ignited the vapors with a match, a jet of blue flame shot out of the jug. Northwestern grad students perform such demonstrations as part of programming for and with local third- and fourth-grade students to help the children see themselves as future scientists.

Submitted by Jenna Logsdon and Su Chen

Do science. Take pictures. Win Money. Enter our photo contest here.

More Chemistry in Pictures and C&EN stories:

Blue fire

FDA requests safety data on hand sanitizers

[studyingchemistry]

Quadruple bonds

Group 6 dinuclear compounds have been of interest have been of interest for over 40 years due to their formation of metal to metal quadruple bonds, σ2π4δ2 [1], with bond order ranging from 0 to 4. The δ bonds are formed from overlap of the dxy orbitals from each metal forming a bonding and antibonding orbital, where z is the internuclear axis. These orbitals are considerably more diffuse and therefore achieve poorer overlap resulting in an order of bond strength of σ> π> δ.[2]

A pair of d4 transition metals can achieve a bond order of 4[1] by filling the σ, π and δ bonding orbitals with no extra electrons in the anti-bonding orbitals, such as in [Re2Cl4].[2]

This is in contrast to the bond orders found in organic chemistry which ranges from 0 to 3, which is a direct consequence of the number s and p orbitals used in bonding.

 Figure 1.[3] (a) Paddle-wheel structure of a dinuclear compound with 4 bridging ligands, Mo2X4 such as [Mo­2­(O­­2CCH3)4]. (b) Structure of Mo2X8 such as K4[Mo2Cl8].2H2O. © Structure of Mo2X4L4 with D2h symmetry.[4,5]

Quadruple bonded metals then form 4 further bonds to ligands, depending on the nature of the ligands, this creates different structures. [Mo­2­(O­­2CCH3)4] has a quadruple bond, high in electron density, is of particular interest due to its particular, due to its unique paddle-wheel structure, spectroscopic properties and potential to be used as a reducing agent.[6]

Over a thousand Mo-Mo compounds have been reported and structures determined using various analytical techniques such as Raman spectroscopy[7], NMR[8] and X-ray crystallography.[1] The Mo-Mo bond length has been extensively researched. The bond length, and thereby bond strength has been determined by X-ray crystallography for 467 compounds containing a Mo-Mo quadruple bond, of which, 442 were within the range 2.06 Å- 2.07 Å.[1] Aforementioned compound [Mo­2­(O­­2CCH3)4] has a Mo-Mo bond length of 2.09 Å [1] and K4[Mo2Cl8].2H2O has a Mo-Mo bond length. [1] This experiment aims to investigate a series of dinuclear Mo compounds containing quadruple bonds and to characterise using NMR and IR.[4]

One of the uses of NMR is to investigate the arrangement of ligands in structure C, Mo2X4L4such as {Mo2Cl4[(C4H9)3]4}. The cis- and trans- forms are of two different symmetry groups and therefore are expected to have different NMR spectrum.[5]

Bibliography

Keep reading

[kemmydoeschem]

Some O-Chem reactions and mechanisms

[kemmydoeschem]

Some O-Chem reactions and mechanisms

[quizzicalcuisine]

A graphic I decided to make in order to compile some of the most important chemicals responsible for the natural smell and taste of some fruits (among others such as butter, lavender, etc.). Feel free to share :)

[bunchareactions]

Fun fact: Ethyl Lactate and Isopropyl Acetate are both green solvents!

[cenchempics]

MORE THAN MEETS THE I

Some molecules produce different colors in different solvents, a phenomenon called solvatochromism. For example, molecular iodine (I2) is yellow when dissolved in water (bottom layer in these funnels) and bright violet when in a nonpolar solvent such as hexane (top layer). In this demonstration, the aqueous layers have increasing concentrations of KI going left to right. KI pulls more I2 into the aqueous layer through a reaction that forms I3–. As a result, the water layer on the right is the darkest yellow, while its corresponding hexane layer is the lightest violet. This reaction is an important part of certain experimental solar cells, which use the interconversion of I3– and I– to pass charge between excited dye molecules and electrodes.

Submitted by Brian Wagner

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Related C&EN Content: A Solid Solar-Cell Solution

Quantum dot solar cells hit record efficiency 

Better Dye Yields Better Solar Cell

[kemmydoeschem]

From yellow to hot pink 😍😍😍 (titration of 0.14 M Tris with 0.1 M HCl using a methyl red indicator)

[microscopicvision]

Credit: Arthur Strange BIOARTS Scarborough, Ontario, Canada

Subject Matter: Citric acid dissolved in alcohol (25x)

Technique: Polarized Light and Rheinberg Illumination

[bombushuntii]

What do you do when you get a new tablet but don’t have time to draw because you have studying to do?

Why, you make study guides, naturally.

This is actually going to be the first in a full set of reference charts (in all subjects) that I intend to keep for future use. The nice thing is that, since they’ll be on my computer, not on paper, they won’t take up physical space and will be easy to keep track of and hard to lose. If for any reason I need a hard copy, I can always print them up.

This one is a guide to common functional groups. Yes I know my colour coding doesn’t make much sense but I was colour coding more for the sake of using pretty colours than for actual study purposes so I’m okay with it.

P.S. If anyone who’s actually good at organic chemistry sees any mistakes in this please please please tell me because I plan to keep this forever as a reference.

[Edit] I’m totally fine if anyone wants to keep this and use it for their own reference as well :)

[dimethylsulfoxide]

Hello people wanting a table and help to name things???