Hello chemistry lovers!
Sorry for the delay with the post. Today we will talk about phenols in chemistry and one new E-number. Phenols are hydroxyl groups (OH-groups) that bind to aromatic compounds where there is a benzene ring (a hexagon). This structure can consist of one or more OH-groups and the simplest phenol only has one hydroxyl group that sticks this way, and you write it as C6H5OH. The oxygen is a bit isolated and directly attached to the benzene ring, and hydrogen is only binding to the “O”. In chemistry, if the name of the chemical ends with “-ol”, then we are talking about an alcohol, but still phenols aren’t alcohols. We can talk about alcohols in the next post. An example of a more complicated phenol is 2-ethylphenol. Here we find a substituted benzene ring (you say that when that ring isn’t on its own), and one hydroxyl group (on carbon number 1) and one ethyl group, CH2CH3 (on carbon number 2) is holding on with single bindings.
The oxygen in the structure switch easily from a single bond to the closest carbon, to a double bond, depending on if the hydrogen is on its right place or if it detach from oxygen (leaving it with too many loose electrons). The part that is probably most fascinating about phenols, is when the pi-bonds, the covalent bonds, are moving around and the double binding between two carbons do shift place, because that specific bond jumps forward and forward. That’s because of the electrons that came from oxygen (there was 2 pairs of electrons loose, sometimes 3 pairs loose, when oxygens own hydrogen went off). The electrons don’t stay still, they move around in the benzene ring, and give one carbon at the time a negative charge. When the electrons do that, then they put too many bonds on one carbon and the structure shift. Very soon I will calculate the KA-value and pka number for different phenols and acids, and learn even more about phenols that are secondary metabolites/products produced in plants!
Now, one example reaction involving phenols: C6H5OH (phenol) + 3 Br2 (aqua) à C6H2Br3OH (2,4,6-tribromophenol) + 3 HBr. The product is a hexagon made of carbons with a Bromine atom on the carbon number 2, 4 and 6, and of course a OH-group on carbon number 1. We also got some hydrogen bromide that is inorganic (this is mostly about chemical compounds without carbons included) and it’s a gas without color that is for example used for production of hydrobromic acid used in laboratories, and it’s also one of the strongest acids known. Phenols in general behave like weak acids, and if we look on the simplest phenol with only one hydroxyl group attached, then we see that H+ is easily released, and a bit lonely oxygen gets a negative charge. This reaction goes a lot back and forth in a solution, with the H^+ attaching and detaching from the rest, like this: C6H5OH (phenol) ßà C6H5O- (phenoxide ion) + H^+
Now let’s talk about a new colorant in food, that is called carmoisine. The colorant today will be of an artificial kind. Curcumin was instead a natural colorant. E122 in question gives a red color to for example confectionary, marzipan, but is used in alcoholic beverages also. Sensitive people should avoid E122, because this additive can give allergic reactions. This colorant lies in the azo dye group. We have E-numbers that are dyes or lakes. Dyes dissolve in water but not in oil. Lakes are oil dispersible (finely divided in oil). All azo dyes are popular for companies because they are cheap to produce, and the product is very stable. What means “stable” in a chemical structure like this (picture below)? This is about how well the resonance is working inside the molecule. Resonance is about how the pi-bonds will be kicked forward thanks to too many bonds on a carbon atom. In general, it is a good thing when there are two or more oxygens in a molecule during resonance (oxygen is a strong carrier of negative charges), that gives a balance over-all (stability)!
Carmoisine is often used when the food molecules are going through great stresses because we are talking about the processing processes/freezing, milling, putting in colorants. After we heat-treat the food, we put in carmoisine to give it back the right color to increase palatability. In slightly larger packages filled with Carmoisone (which comes into companies), we see the warnings text; “Causes skin irritation. Causes serious eye irration. May cause respiratory irritation.” Carmoisine is also a disodium salt, and a compound like that have two sodium atoms (I post two pictures of different salts that show us how disodium salts can look like). Azorubine (as E122 is also called) originate synthetically from coal, and it has a pair of naphthalene subunits. These are based on coal, so these are studied in organic chemistry. Naphthalene looks like 2 hexagons sitting together, there are 10 carbons in total, and the formula for this is C10H8.
https://www.cdhfinechemical.com/images/product/msds/43_120975767_CarmoisineA-CASNO-3567-69-9-MSDS.pdf
https://www.sigmaaldrich.com/SE/en/product/sial/52245
http://foodconstrued.com/2013/09/carmoisine/
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