Introduction to chirality (handedness), and how chirality is related to the groups bonded to a central carbon. Created by Sal Khan.
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L-form and D-form, are how the molecule "bends light". R- and S- designation, are shorthand to distinguish between the two enantiomers, left or right handedness of molecule. Eg, when the smallest side group attached to a chiral carbon, is placed at rear of molecule, then the three other groups may rotate clockwise (R-), or anticlockwise (S-), going from heaviest side group, to second heaviest, then third.
Oggston discovered that nature can tell the difference between 2 different, and two similar side groups, by the nature of attachment. The example Biochemists quote is cis-aconitate in TCA cycle. Might well apply to Glutamic acid, eg MSG. Hope it wasn't synthetically sourced, Chemists just don't get 100% Yields in such reactions (Racemisation)!!!
Chiral centres are applicable in amino acids, though some are likely to be Oggston's 3-point attachment theorem. Hence, they are essential in enzymes (in nature L-form). So, primary, secondary, tertiary structures of enzymes would be altered by D-form, I believe.
Apparently this free drawing blackboard software is quite popular, as I have seen it used by Stanford online courses as well. Newsflash: it sucks. It is painful to watch instructor slowly handwriting words letter by letter. Look, there is a keyboard where you can type it. Or better yet, reveal the whole word or phrase at once. Like powerpoint slides do.
Makes me think of a short story by Arthur C Clarke about a man who accidentally fell into a 4th dimension of space, resulting in all his molecules changing chirality. The result was that he could not attain nourishment from anything he ate and so started starving.
No but that's an easy mistake to make. Look closely at the planes in which each of the three groups below the carbon are in. If you looked at it from above (looking downward through the fluorine and carbon) you would see the molecules arranged methane, bromine, hydrogen (counterclockwise) on the left compound. If you looked down on the other it would be methane, hydrogen, bromine. If you rotated the left compound one "tick" counterclockwise, you would have the bromine in back and the hydrogen on the left.
It's methyl. When considering identifying a group you just identify what protrudes from the central Carbon...since only CH3 protrudes from the central Carbon than it is only a Methyl. If you were to name the molecule though it would be Ethyl: 1-Bromo-1-Fluroehtyl (the rules for naming molecules IUPAC and naming groups can be a bit tricky and requires work to learn)
visualising this with a set of model molecules is maybe a little easier to understand. The main point I see is the emphasis on a plausible product created in a mirror image, perhaps even structurally exactly the same, however, because of its orientation spatially (3D) it can not be placed (superimposed) back onto the original substance no matter how you try to spin it around etc. These differences lead into important theories relative to reactivity and R and S configurations
Think about your own hands and not the drawing... if you were to put your left hand on your right hand, your nails on one hand would be towards you, and your nails on your other hand would be away from you.
Sal I hope you know that you are an inspiration to millions of students around the world watching your videos everyday. I really wish you the best and may you succeed in everything you wish to accomplish
Although foreigners may now invest in A-shares, there is a monthly 20 percent limit on repatriation of funds to foreign countries.
Performance of A-shares.
Since its inception in 1990, including a major reform in 2002, the index has seen great fluctuations. Overall, however, it has grown along with the Chinese economy. The years 2015 to 2016 were a particularly difficult period, with a 52-week performance of -21.55 percent as of July 20, 2016.
As China grows from an emerging market to an advanced economy, there is substantial demand for Chinese equity. Stock exchange regulators continue efforts to make A-shares more broadly available to foreign investors and have them recognized by the global investing community.
In June 2017, the MSCI Emerging Markets Index announced a long-awaited decision it would add stocks to its index. According to CNBC, MSCI will add 222 China A Large Cap stocks to its benchmark emerging markets index gradually beginning in 2018. The MSCI website reveals the stocks it will list include the Bank of China, China Merchants Bank, Guotai Junan, Ping An Insurance, according to a document on Tsingtao Brewery, SAIC Motor, Suning Commerce and Spring Airlines.
Current Dividend Preference.
Participating Preferred Stock.
Convertible Preferred Stock.
Cumulative preferred stock includes a provision that requires the company to pay preferred shareholders all dividends, including those that were omitted in the past, before the common shareholders are able to receive their dividend payments.
Non-cumulative preferred stock does not issue any omitted or unpaid dividends. If the company chooses not to pay dividends in any given year, the shareholders of the non-cumulative preferred stock have no right or power to claim such forgone dividends at any time in the future.
Participating preferred stock provides its shareholders with the right to be paid dividends in an amount equal to the generally specified rate of preferred dividends, plus an additional dividend based on a predetermined condition. This additional dividend is typically designed to be paid out only if the amount of dividends received by common shareholders is greater than a predetermined per-share amount. If the company is liquidated, participating preferred shareholders may also have the right to be paid back the purchasing price of the stock as well as a pro-rata share of remaining proceeds received by common shareholders.
Significance to Investors.