Eu vou denunciar o crime.

Yes. In Brazilian Portuguese, subject pronouns are often omitted when the verb already makes the subject clear.

So:

• Eu vou denunciar o crime.
• Vou denunciar o crime.

Both are correct.

Including eu can add:

• emphasis: I’m going to report the crime.
• contrast: Eu vou denunciar, mas ele não.
• clarity, if needed in context

In everyday speech, dropping eu is very common.

Because ir + infinitive is one of the most common ways to talk about the future in Brazilian Portuguese.

• Eu vou denunciar o crime. = natural, common spoken Portuguese
• Eu denunciarei o crime. = correct, but more formal, stiff, or literary

So even though Portuguese has a simple future tense, Brazilians often prefer:

• vou falar
• vou fazer
• vou denunciar

This is very similar to English I’m going to report.

Denunciar usually means:

• to report
• to denounce
• to accuse/report to the authorities

In this sentence, it most naturally means to report the crime, especially to the police or another authority.

A useful nuance:

• denunciar um crime = report a crime
• denunciar alguém = report or turn someone in
• denunciar corrupção = expose or denounce corruption

So it is stronger and more official than just casually mentioning something.

Because denunciar normally takes a direct object.

So you say:

• denunciar o crime
• denunciar o suspeito
• denunciar a fraude

Not:

• denunciar ao crime ❌

If you want to say to whom you are reporting it, then you may add that separately:

• Vou denunciar o crime à polícia.

Here:

• o crime = the thing being reported
• à polícia = the authority receiving the report

Portuguese often uses articles where English may not.

So o crime can mean:

• the crime
• that crime
• a specific crime already understood from context

Using the article sounds natural in most normal sentences.

Without the article, crime sounds more generic, abstract, or like a headline/category in many contexts.

Compare:

• Vou denunciar o crime. = I’m going to report the crime.
• Crime deve ser punido. = Crime must be punished.
  Here it is generic, so no article is more natural.

Yes, crime is masculine:

• o crime
• um crime

You know here because of the article o.

This is useful because noun endings do not always tell you the gender clearly. Words ending in -e can be either masculine or feminine, so it is best to learn the noun together with its article:

• o crime
• a cidade
• o nome
• a noite

In Brazilian Portuguese, vou is pronounced roughly like voh with a light w-like glide at the end.

A rough English approximation is:

• vou ≈ voh/voo blended quickly

It is not exactly like any one English word, but it is close to the vowel in go, depending on accent.

The whole sentence is roughly:

• eu vou denunciar o crime
• eh-ooh voh denoon-see-AR oo KREE-mee

That is only an approximation, but a few key points help:

• denunciar is stressed on the last syllable: -ar
• the r in crime is the Portuguese tapped/flapped r
• eu is often pronounced very quickly

Often very weakly, and in casual speech it may sound like it disappears.

So:

• careful speech: denunciar
• casual speech in much of Brazil: something closer to denunciá

This is only a pronunciation change. The spelling stays denunciar.

That means vou denunciar o crime may sound more like:

• vou denunciá o crime

This is normal in everyday Brazilian speech.

Yes, both are grammatically correct.

• Eu vou denunciar o crime. = most common in everyday speech
• Eu irei denunciar o crime. = correct, a bit more formal
• Eu denunciarei o crime. = correct, more formal, official, or literary

If your goal is natural spoken Brazilian Portuguese, vou denunciar is usually the best choice.

They change how specific the noun is.

• o crime = the crime; a specific one understood from context
• esse crime = that crime / this crime you just mentioned
• um crime = a crime; not yet specific

Examples:

• Vou denunciar o crime.
  The listener already knows which crime you mean.

• Vou denunciar esse crime.
  More explicitly points to that particular crime.

• Vou denunciar um crime.
  You are introducing it as new information.

Often yes, especially for reporting wrongdoing, abuse, corruption, or a crime.

But depending on context, Portuguese may use other expressions too:

• denunciar o crime = report the crime
• registrar uma ocorrência = file a police report / register an incident
• fazer um boletim de ocorrência = file a police report
• comunicar = communicate/inform, more neutral or formal

Also, be careful with near-synonyms:

• delatar often means inform on / turn someone in, and can sound more like snitch on
• reportar exists, but in Brazil it can sound technical, bureaucratic, or influenced by English depending on context

So in this sentence, denunciar is a very good and natural choice.

In more formal Portuguese, you could use an object pronoun:

• Vou denunciá-lo.

That literally means I’m going to report it.

Notice what happens:

• denunciar + o becomes denunciá-lo

But in everyday spoken Brazilian Portuguese, people often avoid these attached object pronouns and may prefer something like:

• Vou denunciar isso.
• Vou denunciar esse crime.

So denunciá-lo is correct, but it sounds more formal or written than many learners expect.

The normal word order is:

• Eu vou denunciar o crime.

But Portuguese allows some flexibility, especially for emphasis.

Common natural versions:

• Eu vou denunciar o crime.
• Vou denunciar o crime.

Less neutral, more emphatic or marked:

• O crime, eu vou denunciar.

That last one is possible, but it sounds like you are emphasizing the crime specifically. For a learner, the basic order is the safest and most natural choice.