I. Infinitive phrases are phrases (not a complete sentence with a subject and verb) that contain an infinitive preceded by "zu." These phrases are often introduced by verbs or expressions such as "veruschen'(=try), "vergessen"(=forget), "versprechen"(=promise) "anfangen," "vorhaben"(=plan), "Zeit haben."

Frau Mayer versucht, ihr Haus zu verkaufen

Ms. Mayer is trying to sell her house.

Hast du Zeit, heute abend ins Kino zu gehen?

Do you have time to go to the movies tonight

NOTE: zu+infinitive always stand at the END of the infinitive phrase.

With a separable prefix ver b, "zu" is placed beween the prefix and the verb.

Vergiß nicht, mich anzurufen Don't forget to call me.

Sometimes "zu + Infinitive" =English verb + ing

Hast du Lust, mit uns ins Restaurant zu gehen.

Do you feel like going to the restaurant with us

II. Infintive Phrase introduced by "um"

"Um" can introduce an infinitive phrase to indicate purpose or intention. It is NOT used as an accusative preposition. Rather, it is the equivalent of the Eng. Expression "in order" (+ to)

Ich bin zum Supermarkt gegangen, um Lebensmittel zu kaufen.

I went to the supermarket to buy groceries (or food)

"um…zu" phrases can be likened to sentences with the modal verb "wollen"

Ich gehe zum Supermarkt. Ich will Lebensmittel kaufen.

Ich gehe zum Supermarkt, um Lebensmittel zu kaufen.

The verb "wollen" disappears when the second sentence is changed into an infinitive phrase. Wollen indicates intention, so its function is taken over by the 'um …zu" construction(which also indicates intention or purpose.

III. Infinitive Phrases +ohne or (an)statt

When an infinitive phrase begins with ohne(=without) or (an)statt)(=instead of), you indicated what you are not doing/going to do.

Er geht, ohne uns "Auf Wiedersehen" zu sagen.

He's leaving without saying goodbye.

Compare:

Er geht. Er sagt uns nicht "Auf Wiedersehen."

The infinitive construction with "ohne" or "(an)statt" takes the place of sentence with a negative (usually "nicht or "kein"). If you cnage a sentence with a negative into an infinitive phrase, the words "ohne" or (an)statt" take the place of the negative (nicht/kein).

Wir sind in die Kneipe gegangen. Wir haben keine Hausarbeit gemacht.

Wir sind in die Kneipe gegangen, statt Hausarbeit zu machen

We went to the bar instead of doing house work.

Note that the English equivalent is verb+ing (saying, doing)