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Mancude rings and annulenes
What do the structures (a), (b) and (c) have in common? (a)(b)(c) [18]annulene cyclooctadeca-1,3,5,7,9,11,13,15,17-nonaene (PIN) 1,3,5,2,4,6-triazatriphosphinine thiophene Well, it is obvious that...
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Hantzsch-Widman names
Are you tired of carbocycles? Let’s have some ring diversity, I say. Structures that contain two or more different elements in a ring are called heterocyclic. Perhaps because “heteroatom” is really an...
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The many names of crowns
What is the best way to name the structure (a)? (a) 1,4,7-trioxonane (Hantzsch-Widman) 1,4,7-trioxacyclononane (replacement) cyclo[tri(oxyethylene)] (organic macrocycle) 9-crown-3 (Pedersen)...
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Bicycles
How many rings has the structure (a)? (a) diphenyl ether (functional class) 1,1′-oxydibenzene (multiplicative) phenoxybenzene (substitutive) Why, there are two, you’ll say. Anybody can see that. And...
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von Baeyer names
Here’s a cute little structure: (a) housane (trivial) bicyclo[2.1.0]pentane (von Baeyer) Drawn like this, (a) looks like a little house and, indeed, is known as a housane. Alexander Senning called...
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Fused ring names
(a) furan (trivial, retained) oxole (Hantzsch-Widman) Knowing that the structure (a) is called furan, let’s name the structure (b).(b) 2-nitrofuran (substitutive) Easy: 2-nitrofuran. Keeping that in...
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Spiro names
Observe the structure (a). Doesn’t it look like our old friend housane after a tornado? It kept its roof but only just. (a) spiro[2.3]hexane spirohexane Let us number it in the following fashion: (a)...
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Ring assemblies
How shall we call the structure (a)?(a) biphenyl (trivial) 1,1′-biphenyl (ring assembly, PIN) phenylbenzene (substitutive) We can name it substitutively, i.e. substituting one hydrogen atom in the...
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Phane names
Have a look at the structure (a). (a) calix[4]arene (trivial) pentacyclo[19.3.1.13,7.19,13.115,19]octacosa-1(25),3(28),4,6,9(27),10,12,15(26),16,18,21,23-dodecaene (von Baeyer)...
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Inorganic chains and rings
Let’s name a simple inorganic chain (a): (a) 1,2-dinitrosodioxidane (substitutive) bis(nitrosyloxygen)(O—O) (additive) 2,5-diazy-1,3,4,6-tetraoxy-[6]catena (ICR) The shortest systematic name I can...
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λ-convention
The whole edifice of substitutive nomenclature is based on concept of parent structures, most importantly parent hydrides. Implicit in parent hydrides are the valencies, or bonding numbers, of...
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Boron hydride nomenclature
Can we expand the parent hydride naming philosophy much beyond organic chemistry? Not going too far, let’s have a peek at carbon’s immediate neighbour in the periodic table, boron. (a) BH3 borane...
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Polyhedral symbols and configuration indices
Although structural descriptors such as we’ve seen in the names of boron hydrides, for example catena or closo, provide information on atomic connectivity, they tell us little or nothing about the...
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Enantiomers
Have a look at the structures (a) and (b). (a)(b) (+)-amphetamine (trivial) d-amphetamine (trivial) dextroamphetamine (trivial) dexamfetamine (INN) (2S)-1-phenylpropan-2-amine (substitutive)...
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cis and trans
What’s the difference between the structures (a) and (b)? (a)(b) (2Z)-but-2-ene (PIN) cis-but-2-ene (2E)-but-2-ene (PIN) trans-but-2-ene Why, isn’t it obvious: in the former structure, the two methyl...
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Axial chirality
Have a look at the structures (a) and (b). They are the stereoisomers of laballenic acid, with (a) is naturally occurring in plants of the Lamiaceae family. What kind of stereoisomers are they? (a)(b)...
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Planar chirality
In most organic chemistry textbooks, double bond cis/trans isomerism is exemplified by alkenes. It is also observed in cycloalkenes such as cyclooctene that can exist as either cis(a) or trans(b)...
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α, β, ξ
Here’s a molecule everybody must have heard about: testosterone(a). (a) testosterone (INN) 17β-hydroxyandrost-4-en-3-one (fundamental parent + substitutive)...
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α and β again
The descriptors ‘α’ and ‘β’ are also used in carbohydrate nomenclature to specify configuration of cyclic monosaccharides [1, P-102.3.4.2.1]. You may remember that aldehydo-glucose, the open-chain...
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Descriptors, prefixes, combining forms
Systematic chemical names are created, at least in part, on paper, and probably were never meant to be pronounced. It is not only about the length: locants, descriptors, punctuation marks and...
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Oxoacids and their anions
Many of the chemical names referred today to as “common” or “trivial” — as opposed to “systematic” — at the time were very much systematic. Many of them, in fact, remain systematic because there is a...
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Ants, apples, amber
Let’s turn our attention now to other kind of acids. You know what I’m talking about: carboxylic acids. Here’s the simplest one (a): (a) HCOOH formic acid (common, PIN) methanoic acid (substitutive)...
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Hydrogen names
Let us come back to inorganic oxoacids and their anions. Observe the structures (a) through (c): (a)(b)(c) [CO(OH)2] carbonic acid (common, PIN) dihydrogencarbonate (simplified hydrogen)...
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One-electron carbon—carbon bond
What is a covalent bond? We learn in school that it is a chemical bond formed by shared pairs of electrons between atoms. The Gold Book provides a bit more careful definition: A region of relatively...
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Seniority criteria
Last time I took part in the Intra-Universal Panel of Astronomical Chemistry, I had a most edifying and enjoyable discussion with an alien (to me) colleague who, for reasons unknown, showed an...
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