She did know his phone number, otherwise she would phone / would have phoned him.

[Tan Elaine]

1. She did know his phone number, otherwise she would have phoned him.

2. She did know his phone number, otherwise, she would phone him.

Which sentence is correctly phrased? I think sentence 1 is correct. Am I right?

Thanks.

[5jj]

Neither is possible. 'Otherwise' requires a 'not' in the first clause.

[Tan Elaine]

Thanks, Fivejedjon. The 'not' has been advertantly left out.

1. She did not know his phone number, otherwise she would have phoned him.

2. She did not know his phone number, otherwise, she would phone him.

Which sentence is correctly phrased? I think sentence 1 is. Am I correct?

Thanks.

[SoothingDave]

They're both grammatically correct. They mean different things.

(I would use "call" as the verb instead of "phone.")

[5jj]

The 'not' has been inadvertantly left out.

1. She did not know his phone number, otherwise she would have phoned him.
2. She did not know his phone number, otherwise, she would phone him.

Which sentence is correctly phrased? I think sentence 1 is. Am I correct?

Yes.

#2 would be: She does not know his phone number; otherwise she would phone him.