The AMC channel on cable is running a series called Breaking Bad. It is about a high school chemistry teacher who, for various reasons, begins to make high quality methamphetamine with a former student. It is actually quite interesting to watch. Never before have I seen so many details of chemical synthesis on an entertainment tv program.
The 2nd episode portrays a lecture on chirality to a chemistry class. The technical details seem well researched and the dramatic situations are unexpected and novel. I have to say that it is quite well done.
The teacher is a kind of anti-hero. We can identify with him to a point. But where we depart from him is where he breaks bad. The scenes of a chemist working in a respirator and tighty-whities may frighten some viewers. Caution is advised.
Lamentations on Chemistry 
Given: An undistorted (angles and bond lengths) tetrahedral sp3 carbon atom bearing four rigorously identical groups each freely rotating in space. No other structure or functionality is present, no external fields, etc. Said carbon atom, in dilute gas phase, is chiral.
Provide a discrete example or the general case. “8^>)
I assume that you mean instantaneously chiral due to collisions perturbing the symmetry, as with methane. Are you suggesting something else? Are you suggesting that the bulk material may have an overall excess of an enantioner?
I caught the first episode at the very beginning while channel surfing last week. Man was I lucky, this show is great. Second episode aired last night and it didn’t disappoint.
Undistorted CX_4 and it is chiral. Permanently chiral. Sits in a bottle on the shelf chiral. 100% ee and permanent optical resolution at room temperature chiral. Progressively rotates the plane of linearly polarized light in homogeneous solution chiral. Permanent four C_3 and three C_2 axes. The molecule and its mirror image are not surposable. Specify X as a discrete or general case.
This is the fun stuff! Great for an undergrad final exam extra credit question. Find out if they know what they know.
I guess I am missing something important here. I was under the impression that the symmetry elements precluded the formation of a helical aspect to the oscillating dipole of a chiral species that interacted preferentially with one of the circularly polarized rays. Basically, the speed of light through the molecule is different for each of the two coincident circularly polarized rays, causing one to lag and therefore cause a rotation of the plane of polarization of the rays.
What is the nature of the chirality to which you refer? Is there some other attribute that confers asymmetry?
Single molecule geometric chirality strictly arises from absence of all improper (S_n) rotation axes. Build a methane derivative CX_4 without them. (nudge nudge wink wink)
Optical chirality does not measure geometric chirality. Gyrotropy in homogeneous solution or gas phase must average to zero across the EM spectrum – its magnitude and sign (anomalous dispersion!) both depend on wavelength, e.g., ORD spectra. It’s even worse sold state where gyrotropy arises from three separate sources (pseudoscalar from molecular chirality persists in disordered solution; vector is a property of pyroelectric lattices; pseudodeviator from lattice symmetry). Single crystal silver thiogallate, AgGaS_2 with non-polar achiral tetragonal space group I-42d (#122), has immense optical rotatory power: 522°/millimeter along [100] at 497.4 nm. It isn’t geometrically chiral.
Organic texts are remarkably incomplete regarding chirality. Defining chirality in computable terms has been a nightmare,
Click to access e5030271.pdf
Successfully defining computable chirality is nasty,
http://petitjeanmichel.free.fr/itoweb.petitjean.html
Uncle Al found a tiny error in said mathetmatician’s software by designing a perfectly chiral molecule. Even its methylenes are chiral. Petitjean called it “that devilish molecule!” It took nearly 20 months and nearly two hundred tries to jigger together. Then, it was OBVIOUS, hence chiral CX_4.
It was a slow and ugly way to do the job but nobody else was at the finish line. Neither CAS nor IUPAC could assign a systematic name to it, C27H28 (polycycloalkane no bigger than cholesterol). Stereochemistry software, starting with NIST, was rewritten. Uncle Al does it to annoy. “8^>)
I’m with Al to a point. Single molecules do rotate plane polarized light – they interact with it and rotate it. Polarized light rotation as we observe it is a statistical result – there is a mirror image that rotates it equally and oppositely. With avogadro’s number you have all the random orientations covered. But if it is one, then yes it rotates light. Probably even if I only had a half dozen….
But if you define chiral as superimposable on its mirror image, then CH4 superimposes on its mirror image – as long as you allow rotations…
Chirality is NOT superposable upon its mirror image along one axis (one axis’ coordinates reversed in sign). Strongest is parity – NOT superposable upon its mirror image along all axes (all axes’ coordinates reversed in sign). Weakest is helicity – direction of rotation that reverses with point of view (rotating Earth viewed from the North or South pole). A body with helicity (e.g., an electron) with relativistic velocity is chiral because you cannot get to the other pole for the contrary view. All beta rays are 100% left-handed (Weak Interaction). When they lose energy (velocity) from propagation through matter they rapidly racemize with penetration depth.
Given a regular tetrahedron, color one each of its vertices black, white, red, blue. It is now chiral. Build the mirror image tetrahedron. Now tell Uncle Al which tetrahedron is right-handed and which is left-handed.
Tetrahedral undistorted free-to-rotate CX_4 can be chiral – not in the color sense, but the other way. Be clever about it.
Petitjean’s CHI is a normalized measure of parity divergence, CHI = 0 (achiral) to CHI = 1 (perfectly chiral). Twistane C_10 H_16, is a mostly spherical non-polar lump of alkane with no chromophores, not even a double bond; no optical absorption below 250 nm. It has [alpha]D = 440 degrees! CHI = 0.72.
http://csi.chemie.tu-darmstadt.de/ak/immel/tutorials/chirality/index.html
Enough with chirality! What about the errors? A HS chem stockroom with MULTIPLE gallons of HF? NO WAY! Wouldn’t NaOH or H2SO4 be better to disolve a body anyway?
Spot any others?
I have trouble believing that even conc H2SO4 would dissolve a body. What Walt needs is a large Kjeldahl flask, some 50 % KOH, and a propane burner.
You have to wonder what the hell they could possibly do with that much HF. Crack hydrocarbons? Maybe they had to buy a 4-gallon economy pack from Fisher. Kinda creeps me out. \;-)
I think we are supposed to suspend our disbelief under the code of artistic license.
If you don’t know the fundamentals then how can you build upon them? Consider a resolved R or S chiral group, e.g. sec-butanol. CR_4 and CS_4 are non-superposable mirror-image and opposite parity chiral, e.g., C[(S)-(+)-OCH(H)(CH3)CH2CH3]_4
One cannot systematically name such stereoisomers to indicate chirality of the center carbon. R,S M,P D,L delta,lambda… structural nomenclature utterly fails. The chiral center is an undistorted (bond lengths and angles) tetrahedral sp3 carbon CX_4 in point group T (not T_h or T_d) with no color chirality at all. . Such systems can have CHI = 1 – and that is all but impossible for composition chirality centers.
At some level, the current system of nomenclature works as long as you know the conventions. For most people that is enough. The correlation of + or – rotation to R or S is beyond the theoretical horsepower of most synthesis chemists, me included. You don’t need to be able to determine the rotation ab initio in order to make enantiomerically enriched material.
I have to down load some of these links and sit down with them to try to understand what you are saying. I’ve never gotten into it in that level of detail before.
The mathematical language is all but impenetrable to an outsider. I and Petitjean played with it until I had the AHA! moment and designed chiralane. It is obvious in the math. Afterward.
The recipe for *perfect* parity divergence: chiral molecule with three equal moments of inertia and a convex surface. The math is more rigorous, but that’ll do. Anything convex in point groups T (bad boy [6.6]-chiralane, ring-contracted and -expanded chiralanes, chirolanes (hollow), and six fullerene isomers C44, C52, C92, C100) , O (never did conjure an example), and I (two fullerene isomers, C140 and C260) works.
Chiral mass distribution in a single crystal spherical ball of increasing radius can rapidly (a few angstroms radius) go asymptotic to CHI =1. Of 230 periodic crystallographic space groups 65 can contain locally chiral mass distributions (Sohnke space groups). 11 pairs of those are enantiomorphic space groups in which the *space group* is chiral. Only the quartz group, P3(1)21/P3(2)21, has uniformly calculated CHI asymptotic to 1 with increasing radius in our hands. Tellurium has three atoms in its unit cell. Three atoms define a plane. Tellurium (quartz group!) is maximally parity divergent. (Uncle Al won’t ruin the tale by disclosing the – obvious – boojum).
Now we seek a pair of differential scanning calorimeters at 40 to 50 degees latitude that still perform to 0.1% precision OEM spec between 95 and100 C. General Relativity has two founding postulates that are intolerent of parity divergence… and achiral benzil crystallizes in the quartz group. Bwa ha ha!
OK I figured out the plot. Walt makes some meth with the opposite chirality that either cures lung cancer or binds to meth receptors and acts like naloxone (morphine antagonist to a heroin addict) and blocks meth from the normal receptor allowing Jessie to kick the meth habit.
Am I going to be right?
Do the writers have any scientific creds? Is there a consultant on board?
Holy Crap! I’ve gotten behind. Somebody somewhere in the production of this show has chemistry background. I don’t know who. I’m gonna have to do some serious couch time to catch up.