Alright. So here's an example problem that says at Ph. Two, which is the predominant structure of failing, and we're giving these two p. K S P. K one, which is 9.62 and P k two, which is 2.32 And so we know from our previous lesson videos that veiling is a non polar amino acid with a V shaped our group. And so, looking at all of these are groups down below in our answer options, which are highlighted in blue notice that they all have the same structure and the same V shape. So they all have the correct our group for veiling, and we're going to need to determine the correct answer by determining the predominant structure off Valeant's backbone at a ph of two. And so recall from our previous lesson videos that Alfa Amino groups have. P K is in the ballpark range of about 9 to 10.5, and so PK one here must be the PKK of the Amino Group and also recall that Alfa Car Boxer groups have PK is in the ballpark range of about two and so p k two here must be for the car Boxer group. And we know that we can determine the predominant structure by independently comparing these two p. K s to the ph of the solution. And so we can start with the amino group PK. And so we know that a pH of to is less than the amino group P K, which is equal to 9.62 And so we know from our previous lesson videos that when the pH is less than the peak A that the conjugate acid form predominates and the conjugate acid is a protein ated form and the protein ated form of the amino group is going to be an NH three plus. And so we can eliminate any answer option that does not have an NH three plus for the Amino Group. And so this one notice has an N h two plus, so we can cross that off. And this one just has an N h two so we can cross that off a swell and notice that both option A and D have the correct NH three plus form. And so we're gonna need to look at the car Boxer group next, and so we know that a pH of two is also less than the car boxful PK of two point 32 And so again, when the pH is less than the PK, the conjugate acid form predominates, and the conjugate acid form is protein ated. So we expect our car box a group to be protein ated and so noticed that the car box a group for option A is not protein ated so we could go ahead and cross that off and looking at option D notice that it is protein ated. And so that means that d here is gonna be the correct answer. And that concludes this practice or this example problem. So we'll be able to get some practice in our next couple of videos, and I'll see you guys there.
