Dangling infinitives

The Miss Thistlebottoms of the world are always going on about dangling participles,¹ but few usage experts mention dangling infinitives.² What’s a dangling infinitive? It’s an infinitive, “to” + verb, that is not correctly attached to the agent (a noun or pronoun) that carries out the action specified by the verb. When a sentence starts with an infinitive phrase, the subject of the main clause should be the agent that carries out the action specified by the infinitive:

To prepare an NMR sample, we dissolved the crystals in CDCl₃.

Here the pronoun “we” carries out the action specified by the infinitive “to prepare.” Infinitive constructions also work correctly when the subject is implied, as in an imperative sentence:

To prepare an NMR sample, [you] dissolve the crystals in CDCl₃.

where the implied subject pronoun “you” is doing the preparing.

In scientific writing, however, we tend to use passive voice, especially in the experimental section of a paper; and the use of the passive eliminates the agent that is needed to carry out the action in the infinitive:

To prepare an NMR sample, the crystals were dissolved in CDCl₃.

Now we have a problem: “crystals” is the subject of the main clause, but crystals do not prepare NMR samples. Here are some additional incorrect examples, with suggested revisions in which the dangler has been eliminated:

(1) To derive d[CO₂]/dt at time t, the plot of [CO₂] versus time was fitted to a third-order polynomial.

To derive d[CO₂]/dt at time t, we fitted the plot of [CO₂] versus time to a third-order polynomial.

(2) To ensure accuracy, N₂ selectivity was evaluated only when the NO_x conversion exceeded 10%.

To ensure accuracy, we evaluated N₂ selectivity only when the NO_x conversion exceeded 10%.

(3) To determine the structure of such unusual molecules, they must be isolated and observed directly by means of spectroscopic methods.

Determination of the structure of such unusual molecules requires that they be isolated and observed directly by means of spectroscopic methods.

If the structure of such unusual molecules is to be determined, they must be isolated and observed directly by means of spectroscopic methods.

(4) To reduce indoor concentrations of formaldehyde, new materials are being developed.

For reduction of indoor concentrations of formaldehyde, new materials are being developed.

With the goal of reducing indoor concentrations of formaldehyde, new materials are being developed.

To reduce indoor concentrations of formaldehyde, researchers are developing new materials.

(5) To achieve such temperatures, several strategies, including electrical heating and homogeneous combustion, have been explored.

To achieve such temperatures, investigators have explored several strategies, including electrical heating and homogeneous combustion.

What about this sentence? It seems similar to the other examples, but is it incorrect?

To be detected by microwave spectroscopy, compounds must have a dipole moment.

This sentence is correct as written. The infinitive in the introductory phrase is “to be detected,” and the subject of the main clause, “compounds,” is what is being detected.

You can use  your word-processing software to seek out dangling infinitives . Search for the string “.[space]To[space],” carefully check each instance you find, and revise where necessary.

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¹ Theodore M. Bernstein, Miss Thistlebottom’s Hobgoblins: The Careful Writer’s Guide to the Taboos, Bugbears, and Out-Moded Rules of English Usage (New York: Farrar, Straus, and Giroux, 1971).

² Patricia T. O’Connor is one of the few usage experts to mention dangling infinitives: Woe Is I: The Grammarphobe’s Guide to Better English in Plain English (New York: Grosset/Putnam, 1996), pp. 164–166. See also Matthew Stevens, Subtleties of Scientific Style (Thornleigh, Australia: ScienceScape Editing, 2007), p. 40.