Is the molecule chiral?

Was President Reagan a good president?

Which of those is a hard question and why do you think that?

I would say the first question is not hard to understand but can be hard to answer correctly as it is binary and only one of the choices is correct.  The second question is multi-faceted with some facets having an objective, correct answer and some facets being very subjective.  These questions, I believe, are the most difficult.

This comes up because of the distinct nature of the courses currently underway in our program.  In one, the students are studying the contemporary Argentine experience (they’ll explore similar topics in Chile when we go there).  We’ve also begun organic chemistry.  Organic chemistry is a class that pretty much everyone who takes it agrees is “really hard”.  In reality, like most science classes, those who enjoy them realize they aren’t really hard.  They’re quite straightforward.  To be sure, there is a LOT of information and it all plays off each other but there are a few rules and one can extrapolate from those rules to solve most any problem in the subject.  It’s easy to learn how to work the problem but it takes time, practice and skill to apply the rules.  Once you have invested the time and developed the skill, however, the problems are easy.

That is, a molecule is chiral or it isn’t.  A chiral object is one that is not superimposable with it’s mirror image.  You are chiral.  A featureless wood block is not.  A wood block with grain is.  And so on.  Chirality is a vitally important part of organic chemistry as chiral objects interact with achiral (not chiral) objects equally.  However, they interact with chiral objects differently.   As stated above, you are chiral.  More importantly, the vast majority of molecules that do chemistry – that allow you to convert Cheerios into motion, thoughts and heat, for example – are chiral.

Any chiral molecule can exist as one of two enantiomers.  Why just two possibilities?  Well, how many mirror images do you have?  You have only one, of course.  And what is the mirror image of your mirror image?  That’s you again.  This is true for any object, including molecules.  A chiral molecule can have only one mirror image and, by definition, it is not superimposable (that is, the same) as that mirror image. Thus, a chiral object has one, and only one, enantiomer.  If you re-read the preceding paragraph, you’ll see that these two enantiomers will react differently with a chiral object such as yourself.  This has very serious, and potentially dire, consequences for a person injesting a chiral drug.  One of the enantiomers may be a potent anti-nausea medication and the other a terrible mutagen.  This is at the core of the thalidomide tragedy.

Did you follow that?  Is it hard?  Well, try it out.  Which of the molecules below is chiral?



The dashed line represents a mirror reflection plane.  You can imagine you’ve held up a mirror to the molecules on the left to obtain the molecules on the right. The more familiar pair of enantiomeric hands at bottom can serve as a guide.  In the molecule, lines represent bonds between carbon atoms which are located at the bends in the lines.  A dashed bond between carbon and oxygen shows that the bond is going away from the observer.  A wedged line shows the bond is coming out toward you.  In comparing any two molecules, you can turn them, spin them, flip them, etc. but you cannot break a bond (if you break a bond, you’ve made a different molecule and the comparison fails).

So, which of the 4 molecules shown is chiral?  Remember, a chiral object is NOT superimposable (not the same as) with its mirror image.



Did you get that the top two molecules are the same?  They are mirror images.  But if you turn the molecule on the right counterclockwise 60 degrees, you get the molecule on the left.  They are superimposable.  Mirror images that are superimposable with their mirror images are achiral.  Not chiral.

The bottom two molecules are also mirror images.  However, they are not superimposable.  No matter how you turn one molecule, you can’t get the other structure without breaking a bond.  If the two bottom molecules are not superimposable (and they’re not) and they’re mirror images (they are) then they must be chiral.  The two are said to be enantiomers of one another.

If you got this one right, congratulations!  If not, don’t despair.  While basically all the information you need to answer the question is given in the paragraphs above we typically spend a few weeks on this sort of thing in organic chemistry classes. There are a lot of orgo students, some of whom may well have operated on you at some point, who fail to master this material.

The rules are simple but the application takes some practice.

What of the other question?  Was President Reagan a good president?

That is often seen as an easier question by students.  Yet, books have been written on the subject and there is no definitive answer.  On the one hand that is likely because some of the answer is emotional and an emotional answer can’t really be right or wrong.  There are also two (well, at least two) ways to answer the question:  Was he successful in achieving his goals?  Were his goals “good”?  You might well answer one of those questions yes and the other no.

It seems to me that it is because there is no easy answer that students think this is an easier question.  They can make an argument, craft a response, play both sides, argue if points are deducted.  It is much harder to do this in organic chemistry (or any other science).  The student’s goal is simple: earn a good grade.  Thus, the difficulty of the question becomes: How easy is it to score points?  From this perspective, the presidential question is far easier.  In reality, if one seeks a “true” answer, it is a much more difficult question.

Our last two Argentine classes have looked at the 1976 coup d’etat, life in Argentina under the military junta and the return of democracy.  Our professor claimed that most people, in Argentina and without, consider this in simple terms:  Military was evil, people overcame.  For certain, this is how I thought about it.  He said that we all like to believe this and that it is half correct, the military junta was most assuredly evil.  However, four times previously the military had intervened in Argentina when chaos reigned in the nation and brought about peace and stability.  The democratically elected governments leading up to the 1976 coup were terribly ineffective and the nation was suffering terribly.  From that perspective, one can imagine that the military believed not just that it could take over but that it should.  It ended a disaster but when chaos reigns, the urge to DO SOMETHING is strong.

As to the people overcoming, his claim is more that economic misery is what brought the military government down.  The junta withstood human rights investigations (of which it was very, very guilty) and even losing a war in humiliating fashion.  But the economy was a shambles and that is hard for anyone to ignore.  Is he right?  I don’t know.  I’m not much of a political scientist.  But certainly, Pinochet in Chile came to power similarly, committed similarly heinous human rights abuses and stayed both in power and out of jail for a very long time.  The difference?  The Chilean economy was humming along through much of Pinochet’s rule.  It’s the economy, stupid.

An aside, our professor, whose class I really like, sees many similarities between the 2016 US presidential campaign and Latin American campaigns, especially on Trump’s side.  The Trump campaign was much more about TRUMP and less about ideology.  He carved out certain small groups as to be blamed for most of our problems, spoke in a populist manner rallying his supporters into a new community and promised that only he could solve the problems.  Our professor is a professional professor of political science and I will do a terrible job of relaying the analysis.  But it was a convincing tale.  He further claims that Americans voters are both ignorant of Latin American politics (a fair claim) and/or unwilling to compare ourselves to Latin America (also probably fair).  His analysis has implications that aren’t relevant here, not that the whole aside is, but that the USA is obviously set up differently than Latin American nations, with a different set of political traditions, economic structure, etc. and that the outcome of Trump’s presidency is unlikely to resemble those of Latin American leaders.  But his point is that we should stop drawing comparisons to previous American presidents or European leaders and think more broadly in trying to figure out the new normal in American politics.

It’s okay, he said, Argentina, like the United States, has long tried to distance itself from Latin American and portray itself as being European.  We’ve (the USA) just been better at this than Argentina.


So, what is a hard question?  Is it one that is technically difficult to solve but straightforward and with a single correct answer?  Or a conceptually simpler question that is multi-faceted and with no clear answer?

How you answer, “What is a hard question?” probably says a great deal about how your brain works and where your interests lie.  I would further argue that if you find one type of question easier to answer you should, especially if you’re a young student, work harder on the other type.  Push yourself to attempt questions that aren’t comfortable for you and in that way you’ll grow.




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