When to use "en + infinitive" vs "de + infinitive"?

[createdamadman]

A short story I read had the sentence "Seré la primera en escribir mi nombre en tu yeso."


I asked on Reddit if I could say "de escribir" instead of "en escribir" and these are the responses I received:


1.) I'd probably say "que escribe su/el nombre". No one else is going to write your name.


2.) "Nope, it's totally weird to say that and I think that even grammarly incorrect."


The first response makes no sense to me. Why would you say "que escribe" in this case? The second response doesn't explain why it sounds weird. Context-Reverso shows many examples of "de escribir" being used to mean "to write" (https://context.reverso.net/translation/spanish-english/de+escribir#to+write), so I don't understand why it's wrong.

[Rusty]

The responses you got are correct.

It doesn't make sense to use 'de escribir' in this sentence, the examples you found notwithstanding.

Where 'en escribir' appears, its literal translation is 'in writing', but someone may translate it as 'to write'.
It is perfectly fine to replace the prepositional phrase 'en escribir' with 'que escribe'. Both phrases mean the same thing: the proposed action the person is offering (the first in signing or the first that signs the cast).

Using 'el nombre' instead of 'mi nombre' is the prescribed grammar; since first person is already established, it's redundant to include the first person possessive determiner 'mi'.
If you were there to put someone else's name on the cast, you would say 'su nombre'.

The independent clause, "I'll be the first," can stand on its own, but it begs the question 'in doing what?', especially if signing the cast hasn't already been the topic of discussion.

The crux of the matter is choosing an introductory word for the subordinate clause.

The preposition 'en' can introduce such a clause, a gerund being used as its object, which establishes the action (signing). Gerunds are nouns; the Spanish equivalent is the infinitive.

Another way to introduce the subordinate clause is to use the relative pronoun 'que'. In English, this pronoun is translated as 'who' when the pronoun represents a person. Because the pronoun refers back to 'the first', a third-person conjugation of the action verb is required.

I'll be the first in signing your cast.
I'll be the first who signs your cast.

[createdamadman]

Ah, thank you! This does help.