Can the word "now" be used to connect two independent clauses?

The second definition (from the Oxford Dictionary Online) states: "Used, especially in conversation, to draw attention to a particular statement or point in a narrative."

Example sentence:

I don't like Scotch. Now, if it had been Irish Whiskey you'd offered me.

Can it be used to connect two sentences together like a conjunction, as in the following example:

I don't like Scotch, now if it had been Irish Whiskey you'd offered me.

Is that ungrammatical?

In your example,

I don't like Scotch. Now, if it had been Irish Whiskey you had offered me.

this has two main issues with resultant problems.

1. "Now" can be used as an adverb to connect two independent clauses. This would create a similar situation to although, however, etc. In such a case you can use a period to end your first clause, or you can use a semicolon followed by your adverb +/- a comma.

I don't like Scotch; now, if it would've been Irish Whiskey you'd offered me ...

2. Your second clause is not a complete sentence. In any circumstance, it would not take a full stop. A comma can be used after "now" as above, or it could be used to introduce an if/then construction.

"Can I get you a Glenlivet?"

"I don't like Scotch. Now if it had been an Irsh Whiskey you'd offered me, then I'd say, 'Please, on the rocks.'"