The DNA base thymine dissolves in water due to hydrogen bonding. Which of the following hydrogen bonds drawn between thymine and surrounding water molecules are valid? (LO 8.10) (a) I and II (b) I, II, IV (c) I, II, III (d) III and IV

Video transcript

Hello everyone today. We have the following problem. Small alcohols up to four carbon atoms are completely miserable with water alcohols from hydrogen bonds when dissolved in water identify which one of the following hydrogen bonding interactions between an alcohol molecule and the surrounding molecules surrounding water molecules is correctly drawn. So first we have to determine, we have to define what is hydrogen bonding. So hydrogen bonding in simplest terms is simply when a hydrogen is bonded to an electro negative atom, such as flooring oxygen or nitrogen. So that constitutes hydrogen bonding. It was stated before in the question stem that alcohols can form these hydrogen bonds. Right? And alcohol is specifically this O. H bond. This hydrogen oxygen bond here, that is an alcohol group. And so due to the electro negativity trends, which according to the periodic table, we have electro negativity trends, electro negativity increases as you go up and to the right of the periodic table. And so according to that oxygen is more electro negative than hydrogen. So oxygen gets a partial negative charge while hydrogen gets the partial positive charge. It's also important to note that opposite charges attract so opposite charges attract meaning a positive charge will be attracted to a negative charge and vice versa. With that in mind, we have to look at our following answer choices. An answer choice A. We have this hydrogen, this oxygen here, This electro negative atom bonded to a hydrogen hydrogen and another hydrogen. This is actually very correct. The correct depiction of hydrogen bonding. If you look at your choice be there is this hydrogen hydrogen bond, which is not possible. Remember hydrogen have a partial positive charge. So they would repel each other opposite charges, attract same or like charges repel So answer choice B. Is not our answer. Moving on to see we see that we have one oxygen here bonded to a hydrogen bonded to a hydrogen and it's bonded to an oxygen. However, we have to note that this hydrogen is also bonded to another hydrogen and as we said it before. This is not possible due to the like charges or the partial positive charges on the hydrogen repelling one another. So C. Is not our answer either. If we look at D, we see that we have this oxygen here bonded to a hydrogen bonded to another hydrogen. However, these two oxygen's are bonded towards one another and as you said before, oxygen carries a partial negative charge and like charges repel so answer choice D. Is not her answer, leaving us with answer choice A As the correct answer. Overall, I hope this helped. And until next time