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A plastic ball-and-stick model of proline. In chemistry, the ball-and-stick model is a molecular model of a chemical substance which displays both the three-dimensional position of the atoms and the bonds between them. [1] The atoms are typically represented by spheres, connected by rods which represent the bonds.
The model shown to the left represents a ball-and-stick model of proline. The balls have colours: black represents carbon (C); red, oxygen (O); blue, nitrogen (N); and white, hydrogen (H). Each ball is drilled with as many holes as its conventional valence (C: 4; N: 3; O: 2; H: 1) directed towards the vertices of a tetrahedron. Single bonds are ...
In compounds, fluorine almost exclusively assumes an oxidation state of −1. Fluorine in F 2 is defined to have oxidation state 0. The unstable species F − 2 and F − 3, which decompose at around 40 K, have intermediate oxidation states; [100] F + 4 and a few related species are predicted to be stable. [101]
Several of the CPK colors refer mnemonically to colors of the pure elements or notable compound. For example, hydrogen is a colorless gas, carbon as charcoal, graphite or coke is black, sulfur powder is yellow, chlorine is a greenish gas, bromine is a dark red liquid, iodine in ether is violet, amorphous phosphorus is red, rust is dark orange-red, etc.
Fluorine's chemistry is dominated by its strong tendency to gain an electron. It is the most electronegative element and elemental fluorine is a strong oxidant. The removal of an electron from a fluorine atom requires so much energy that no known reagents are known to oxidize fluorine to any positive oxidation state. [20]
Hydrogen couples with fluorine, which is very typical to see in 19 F spectrum. With a geminal hydrogen, the coupling constants can be as large as 50 Hz. Other nuclei can couple with fluorine, however, this can be prevented by running decoupled experiments. It is common to run fluorine NMRs with both carbon and proton decoupled.
His model predicts that F donates electrons into a vacant atomic orbital in the atom it is bonded to, giving the bonds a certain amount of sigma bond character. In addition, the fluorine atom also receives a certain amount of pi electron density back from the central atom giving rise to double bond character through (p-p)π or (p-d)π "back ...
Electrophilic fluorination is the combination of a carbon-centered nucleophile with an electrophilic source of fluorine to afford organofluorine compounds. Although elemental fluorine and reagents incorporating an oxygen-fluorine bond can be used for this purpose, they have largely been replaced by reagents containing a nitrogen-fluorine bond. [1]