Is there a preferred method to writing organic chemicals by abbreviation?

I am finding it hard to decipher the methods I see in writing.

For example $\ce{EtOH}$ is ethanol, which makes sense, but $\ce{PhAc}$ is acetophenone, where the constituents appear to be backwards.

What about more complicated chemicals like 1,1-diphenylethanol, would $\ce{EtPh2OH}$ be considered appropriate, or maybe $\ce{Ph2EtOH}$?

  • $\begingroup$ The best practice is to avoid abbreviations as much as possible, but when unavoidable to define the meaning of an abbreviation and then stick to it throughout the whole text. $\endgroup$ – Wildcat Sep 26 '16 at 20:37
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    $\begingroup$ Say, if in the beginning of a paper you write: "We studied the reactivity of 1,1-Diphenylethanol (EtPh2OH) bla-bla-bla..." and then use the EtPh2OH abbreviation to mean 1,1-Diphenylethanol to the very end, everything will be fine. $\endgroup$ – Wildcat Sep 26 '16 at 20:45

The only accepted practice without any further constraints is to only use element symbols and sum or constitution formulae. Taking your and a few other examples, that would result in:

  • $\ce{C2H5OH}$ or $\ce{H3CCH2OH}$

  • $\ce{C6H5COCH3}$

  • $\ce{H3C(C6H5)2COH}$

  • $\ce{H3CCOOC2H5}$

  • $\ce{(CH3)3COCH3}$

The more complicated these get the less clear everything is. Thus, many people make use of a set of common abbreviations. However, these must be defined in a list of abbreviations, footnotes or wherever.

  • $\ce{EtOH}$
  • $\ce{PhAc}$[1]
  • $\ce{MePh2COH}$
  • $\ce{EtOAc}$
  • $\ce{$t$BuOMe}$

Where the symbols $\ce{Et, Ph, Ac, Me, $t$Bu}$ would need to be defined to mean ethyl, phenyl, acetyl, methyl and tert-butyl, respectively.

Finally, of course, you can suggest other common or your own abbreviations and use them (consistently!). For example, in my group it is rather common to abbreviate $\ce{EtOAc}$ as $\ce{EE}$ (because of its retained German name Essigester). Or a common way to denote the last compound in that list is $\ce{MTBE}$ or $\ce{TBME}$ (methyl-tert-butylether or tert-butylmethylether). Again, these abbreviations must be defined in footnotes or a list of abbreviations in best practice.

Finally note that an abbrevation typically includes all the hydrogens. Thus, methyl is always $\ce{CH3}$; $\ce{MeCl}$ is permissable for chloromethane but $\ce{MeCl2}$ does not mean dichloromethane. Consequently, neither $\ce{EtPh2OH}$ nor $\ce{Ph2EtOH}$ are permissable for 1,1-diphenylethanol, since carbon $\ce{C{1}}$ has no remaining hydrogens (not 2 as $\ce{CH3CH2}$ — ethyl — would imply).

[1]: Note that $\ce{Ac}$ can also mean actinium. If your paper uses actinium anywhere, do not use $\ce{Ac}$ as an abbreviation for acetyl or it shall cause confusion. The same is true for $\ce{Pr}$ and praseodymium and a few even less common others.

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    $\begingroup$ In addition to Ac (actinium or acetyl) and Pr (praseodymium or propyl), there may also be Cm (curium or carboxymethyl), Nb (niobium or p-nitrobenzyl), Np (neptunium or p-nitrophenyl), and new Ts (tennessine or 4-toluenesulfonyl). $\endgroup$ – Faded Giant Sep 27 '16 at 13:18
  • $\begingroup$ Didn’t know about tennessine, never encountered the nitrobenzyl and nitrophenyl abbreviations afaicr. But thanks @Loong! $\endgroup$ – Jan Sep 27 '16 at 13:29

Generally, you should avoid jargon. Abbreviated terms should be used with care, and their use should be limited to those cases where it is not likely to cause confusion. Therefore, it is often preferable to avoid abbreviations. However, if a long term is repeated many times throughout a text, an abbreviation may be warranted. You may also use abbreviations when it is necessary to prevent awkward construction.

If a list of abbreviated terms is not given in your document, then the first time that an abbreviated term is used, the full term shall be given with the abbreviated term following in parentheses. After defining the abbreviation in the text, you may use it throughout the document. However, if the abbreviation is used in the abstract of a publication, define it at first use in the abstract and again at first use in the text.

2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (binap)

An exemplary list of recommended abbreviations is given in Appendix 10-2 of The ACS Style Guide. This list includes various structural abbreviations that are used in organic chemistry, for example

Ac – acetyl
Me – methyl
Et – ethyl
Ph – phenyl

Note that this list also includes some symbols that are not abbreviations (such as unit symbols or element symbols). The ACS Style Guide also includes a short list of common abbreviations that do not need to be defined (see page 158).

According to the Graphical Representation Standards for Chemical Structure Diagrams (IUPAC Recommendations 2008), structural abbreviations may also be used as labels in structural diagrams. These recommendations also include rules for the preferred ordering of structural abbreviations and other symbols in contracted labels (e.g. $\ce{-CHPh2}$ and not $\ce{-CPh2H}$).

According to the 2008 IUPAC recommendations (see Table II on page 406), the structural abbreviations Me, Et, Pr, iPr, Bu, iBu, s-Bu, t-Bu, Ac, Ph, Ms, Ts, and Cp may be used freely without further explanation. Other structural abbreviations may be used if they are accompanied by a clear explanation (e.g. a graphical representation) of the represented structural fragment. The use of structural abbreviations that are identical to an element symbol (e.g. Ac, Cm, Nb, Np, Pr, and Ts) should be restricted to situations where they are unlikely to be mistaken for the element symbols.

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  • $\begingroup$ That's a wonderful resource! I've read through some of it and realized that I make a lot of common mistakes, whoops! $\endgroup$ – Ryan Ward Sep 27 '16 at 16:13
  • $\begingroup$ @CayetanoGonçalves Note that I included links to two different documents, and both are mainly recommendations. If you deviate from the recommendations, it is not necessarily a mistake. $\endgroup$ – Faded Giant Sep 27 '16 at 16:19
  • $\begingroup$ I was referring to the IUPAC recommendation for structure diagrams, it's very thorough. $\endgroup$ – Ryan Ward Sep 27 '16 at 18:28

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