Explain why, despite the Br-Br bond being weaker than the Cl-Cl bond, the rate of reaction between chlorine and phosphorus is faster than the rate of reaction between bromine and phosphorus (assuming the same allotrope of phosphorus is used, and assuming the same state or phase for both halogens).
Originally posted by jyjyjy:
JJC P2 Q1(e) why is it that even though reaction is independant of [I2], when [I2] is halved, time is halved? wouldn't that be first order?
Q5(c)(iii) How does this mechanism look like? Is it possible for the Br- from step 1 to attack instead?
P3 Q1(b)(ii) Why does the answer state that when the reaction just becomes feasible G=0? Isn't the reaction feasible when G<0? When G=0 isn't it just at equilibrium?
P2 Q5ciii) SN1. If the leaving group Br- attacked back, then you would end up with the original reactant, ie. no net reaction occurred.
P3 Q1(b)(ii) Yes you're right, but what exact value are you going to substitute in for delta G? -1? -0.1? -0.01? -0.001? So just use delta G = 0 first, then state that for the reaction to be thermodynamically feasible, the temperature needs to be higher than 958K (ie. take initiative to improve on the given mark scheme answer, when answering such questions in the A levels).
Originally posted by Earthcosmic2:
Every year ? You mean ever since you ORD'd, you have been taking and re-taking A-Levels every year ? Sounds fun. lol. I want to re-take my A-Level is cos of interest in the subjects like Physics and Maths. Not sure whether I should take the whole combi or not or just the subjects I am passionate in. Sigh ....
Since you're taking A levels out of interest, not out of necessity for University admission, then just take the subjects you're interested in and can self-study for.
To self-study, you can use online resources such as OwlCove.sg (local), TickNinja (local), and of course, internationally acclaimed Khan Academy (international), by Salman Khan, the man who taught himself hundreds of subjects across all levels, and now teach billions of people online for free.
To skip the biochemical-genetic-medical explanations on the whys and hows, go straight to the list of Medicines that may interact with the chemical compounds in Citrus fruits :
Btw, Lee Hsien Loong's effort to combat diabetes in Singaporeans notwithstanding, you should still always go for Regular Coca-Cola over either Coca-Cola Zero or Coca-Cola Light (marketed as Diet Coke in some countries), because artificial sweeteners are always even more unhealthy than natural sugar.
Dr Amy Myers : What is an MTHFR Mutation and What Can We Do About It?
Homocysteine and MTHFR Mutations : relation to Thrombosis and Coronary Artery Disease
Homocysteine : Associated Diseases, Link to Vitamin Bs, Homocysteine Reduction Methodologies
Methylation and Homocysteine : Factors and Treatment
Damned if you do, damned if you don't. Welcome to physical incarnation.
Migraine sufferers have defective MTHFR genes and require High Vitamin Bs intake to reduce Homocysteine levels to prevent Migraines
Medical Study finds Link between High Vitamin Bs intake and Lung Cancer in men
L-Methylfolate (5-MTHF) supplementation required for people who cannot process folic acid due to MTHFR gene mutation
Dr Lynch explains why (6S)-5-methyltetrahydrofolic acid is the correct enantiomer (H2 Chemistry) that is required as supplementation for sufferers of MTHFR gene mutations :
Question : I was wondering about the connection between MTHFR and glutathione you mentioned in your video presentation. It seems to me that if there is a MTHFR defect, resulting in undermethylation, that should result in increased availability of homocysteine to be converted to cysteine, and ultimately to formation of glutathione. Yet you are saying there may be problems with glutathione production in MTHFR mutations. Can you explain why? - A fellow medical doctor.
Dr Lynch replies : Great question. Short term, you are correct. Short term, the increase in CBS enzyme activity should lead â€“ and does lead â€“ to increased glutathione production. The problem is, long term, with MTHFR, and oxidative stress, the glutathione oxidation increases beyond the point of glutathione production. This is because the traditional transmethylation cycle (Methionine cycle) and BHMT pathway help produce CoQ10, carnitine, phosphatidylcholine, creatine, SAMe â€“ all of which are big players in antioxidant production and mitochondrial function. As those decline, oxidative stress increases, CBS upregulation is even higher â€“ and in turn, due to decreased CoQ10, carnitine, creatine, etc, ammonia levels climb and potentially so does hydrogen sulfide levels â€“ and the inability for the sulfonation pathway to keep up with the increased sulfite/sulfide production thus leading to sulfur sensitivity and molybdenum deficiency. I should also add that the likelihood of cysteine, glycine and B6 levels declining are high due to long term oxidative stress. Then â€“ the production of glutathione is also affected. Not to mention the decline of vitamin C, selenium and vitamin E which help prevent oxidized glutathione and help recycle it back into reduced glutathione. I believe that if we support the levels of CoQ10, carnitine, creatine, magnesium, phospholipids, molybdenum, decreased sulfur foods initially â€“ and decreased sulfur supplements â€“ and possibly increase SAMe right out of the gate â€“ before even supplementing with glutathione, methylfolate or methylcobalamin, the degree of improvement should increase quickly. As improvement occurs, then supporting phase 2 with glutathione, NAC and glycine should further help. I think now if we support the MTHFR defects this way â€“ by reducing oxidative stress, improving cell membrane stability and replenishing mitochondrial and antioxidant levels â€“ our patients will improve much faster. Then â€“ once those are in play â€“ then supporting MTHFR for long term natural production and hopefully removing that initial supplementation. - Dr Lynch - https://seekinghealth.org/resource/podcast-8-mthfr-and-glutathione-production/
See Dr Lynch's "Supplements to Reduce Homocysteine Levels"
MTHFR gene, Homocysteine and Vitamin B12 : A comparison of different approaches by Dr. Ben Lynch versus Dr. Amy Yasko versus Dr. James Braly
The 400mg dose used in the medical studies for treating migraines is extremely high, and will cause multiple organ toxicity if you're exposed to sunlight (ie. specifically UV light, also generated by some indoor lighting), as well as upset the balance between the other B vitamins.
Vitamin B2 Riboflavin Can Be Toxic with Sunlight Exposure
"I concur that excessive B2 as well as B1 and B3 can make the need for methylfolate B9 and potassium become insatiable and send Serotonin levels plunging and many other problems. The balance with the other B vitamins has to be found by titrations and varies depending on your genetics." - http://forums.phoenixrising.me/index.php?threads/no-love-of-b2-here-a-warning-about-riboflavin.31639/
On a related medical biochemistry note, in the same discussion thread :
"Why excessive vitamin B2 causes a reduced amount of Serotonin : B2 is used in 3 very important enzyme complexes that are related to energy production, and that also use B1 Thiamine : the pyruvate dehydrogenase complex, the alpha-ketoglutarate dehydrogenase complex, and the branched chain ketoacid dehydrogenase complex (which allows valine, etc, to enter the TCA cycle as intermediates or acetyl CoA). If a person is low on B1 Thiamine, then taking B2 without B1 Thiamine (and you need more of the B1 Thiamine than the B2), they could drive their B1 Thiamine levels even lower because taking B2 will push these enzymes, which also use B1 Thiamine. B1 Thiamine is also used in the Pentose Phosphate pathway, or PPP, which provides NADPH for Glutathione reductase, among many other pathways. With low B1 Thiamine, the NADPH production from the PPP is reduced and then the body has to make up the difference through the Folate cycle. It isn't well known that the Folate cycle can produce NADPH, but it is. When glycine is used to make 5,10-methylene THF, ammonia is released. What do you need to get rid of ammonia? BH4. What is one of the things you need to make Serotonin? BH4. What happens is that the other amino acids are shunted into making serine and glycine for NADPH synthesis and so the urine amino acids are low, except for taurine, which can't enter the TCA cycle. The amino acids enter the TCA cycle and when they become malate they can enter the pathway to make serine and glycine. This is what showed up on my husband's urine amino acids test, with all the essential amino acids very low except taurine. My husband has had minor depression for years, and also high ammonia for years (we can smell it in his sweat and it comes out on urine tests.) It doesn't matter whether he has a high protein or low protein diet, his sweat smells, or smelled, like ammonia. We felt that it might cause a problem with his BH4, but we couldn't see what to do about it. Well, 3 days ago he started taking 1000mg of thiamine, instead of 100mg, along with his other vitamins, and last night he came in after exercising and sweating like crazy, and he said, "My shirt doesn't smell like ammonia now when I exercise!" And it didn't!"
A woman (wiltedflower77) with the following genotypes sought advice regarding her nasty experience with TMG supplementation :
MAO rs6323 +/+
MTHFR c677T +/-
MTRR A66G +/-
CBS A360A +/-
VDR Bsm +/+
SOD2 A16V +/-
"I tried taking about 200mg TMG powder in the morning. By next day I am severely depressed, suicidal, very tearful, and angry. The next day after stopping it I feel better mentally. I just don't understand what's happening???" - http://forums.phoenixrising.me/index.php?threads/tmg-makes-me-very-depressed-why.45321/
In the same discussion thread, a man (Hip) referenced a post he made previously :
"I have worked out the underlying biochemical mechanism why TMG, SAM-e and betaine hydrochloride cause me to feel depressed : http://forums.phoenixrising.me/index.php?threads/just-got-my-methylation-and-detox-profile-results-can-the-experts-kindly-provide-commentary-please.22304/page-2#post-351180"
Originally posted by jyjyjy:
PJC P3 Q4(a) How did they manage to come to the conclusion that G contains basic/amine group and phenol from G reacting w NaOH and HCL? Also how to conclude that K has 2 phenol groups from K not reacting with PCl5?
5(a)(i)Why did the answer key show -1.02V in one line and +1.02V in the next?
P2 Q6 (b) what does it mean by ring/angle strain?
K comes from G, which contains 3 OH groups (since there is no COOH group since G doesn't react with Na2CO3, and the idea of the O atoms being carbonyl C=O groups is inconsistent in terms of degree of unsaturation with the subsequent reaction products implying presence of a benzene ring), 1 of which must be a secondary alcohol (since J reacts with 2,4-DNPH but not with Tollens) which is eliminated during dehydration to form K, hence the 2 remaining OH groups, which don't react with PCl5, must be phenolic OH groups, which is consistent with K being oxidized by KMnO4 to L (use degree of unsaturation to deduce benzene ring oxidation).
Q5ai) The -1.02V refers to standard oxidation potential of tartaric acid to CO2, but the question asks you for standard reduction potential of CO2 to tartaric acid, that's why.
P2Q6b) 3 or 4 membered lactone rings are strained (ie. ring strain), because their angles deviate from the ideal bond angles as predicted by VSEPR theory (ie. angle strain).
Did you know... raw onions, raw garlic and durians have peculiar effects on some people, such as making you thirsty and/or sleepy? Such 'allergic' reactions are genetically determined (by a number of inter-related genes), and are certainly associated with the various metabolic biochemical cycles and systems that we've been looking at, in the other posts here.
Need a clue? What do all 3 (onions, garlic and durians) have in common? Their pungency? Which is caused by? That's right, sulfur-rich compounds (eg. proteins rich in cysteine amino acid).
As you should know by now (reading my other posts in my Health Hacks forum), Glutathione is a key anti-oxidant which requires the sulfur-containing cysteine amino acid (which is why N-AcetylCysteine is often used by medical doctors to replenish a patient's Glutathione levels).
And the metabolic biochemical cycles and systems involved in generating and regulating Glutathione levels, also involve the MTHFR gene, all the B Vitamins, as well as the undermethylation versus overmethylation issue.
It's therefore not surprising, that sulfur-rich foods such as onions, garlic and durians, have such peculiar effects on some people. And what exactly it means for people 'allergic' to these foods, in terms of the MTHFR and associated genes, the undermethylation versus overmethylation issue, is not so straightforward and little understood even by medical doctors at the current time.
spiralgal : Isn't it important to test the SUOX gene, the CBS gene and other genetic SNPs as well? Some people can't eat a lot of sulfur veggies and need to deal with this before going through an MTHFR protocol? I wonder about that when chronically ill people change their diets to a more sulfur enriched veggie diet, but don't feel better and maybe worse.
NEN : I agree it is important to test for other genetic SNPs. My doctor tested me for MTHFR and found I had one copy. But the more I supported myself with sulfur-rich foods and supplements the worse I felt. After doing the 23-and-me genotyping I learned I was CBS homozygous and had several other serious mutations. When I backed off the high sulfur diet and changed up my supplement protocol I had a dramatic improvement in symptoms.
MissBloat :I was diagnosed with Leaky Gut 6 months ago and have seen been on a very strict, clean diet, and have detoxified my life. My symptoms have, however, worsened substantially. I have been feeling so confused and disheartened by my progress. Recently, I did 23andMe and am heterozygous MTHFR, heterozygous CBS A360A and homozygous CBS A360A. My diet has been very high in sulfur and I wonder if that may be contributing to the problem. It seems the healthier I eat, the more sick I feel!
Mandy : I recently found out that I have CBS mutation, which explains why I felt terribly poorly when I juiced supposedly healthy broccoli and kale (this was before I did the genotyping). It took me really, really long to figure this contradiction.
[Chemistry / Physics] - A-bombs vs. H-bombs: What's the difference?
Many restaurants in Singapore use bleach to wipe tables and mop floors even when customers (eg. myself) are present and still eating, the bleach smell has always nauseated me and I've always intuitively known there would be harmful damaging biological effects, even on customers with occasional exposure, let alone clueless, hapless and helpless employees using the bleach (similar to some pitiful employees working under installed UV lightings at their workplace, eg. Singapore Zoo / Night Safari, without realizing the carcinogenic DNA damage UV light causes, which is also why you should get your anti-cancer Vitamin D from supplements rather than from sunlight exposure, no thanks to ozone layer depletion).
Regularly using bleach linked to higher risk of fatal lung diseases such as COPD
Related to the previous post above, sodium hypochlorite [Latin name] or sodium chlorate(I) [Stock name] is often used as the active oxidizing ingredient in most Bleach solutions (this varies with brand). NaClO is obviously an ionic compound, which is thus non-volatile. Yet, you can certainly smell Bleach, and the vapors have now been shown in medical studies to cause irreversible oxidative damage to your lung alveoli tissue, resulting in severe lung diseases such as COPD. Explain this apparent contradiction.
Originally posted by Claresse216:
Hello! May I ask if there is a need to explain why permanent dipole-permanent dipole attractions are stronger than instantaneous dipole-induced dipole attractions when answering a qn asking for the reason in difference in melting/boiling point of different molecules? If yes, what should I include?
No need to explain further.
If one species has intermolecular hydrogen bonding while the other only has intermolecular van der Waals interactions, there is no need to specify the type of van der Waals interactions.
If both species only have intermolecular van der Waals interactions, then the most important point to consider (ie. which outweighs the polarity factor described next) is the size of the molecule and total number of electrons in the species.
Only if both species have similar molecular size and total number of electrons, then you consider the polarity of the 2 species, and bring in the type of van der Waals (ie. only for similar molecular size and number of electrons, then Keesom van der Waals forces outweigh Debye van der Waals forces outweigh London dispersion van der Waals forces).
Another factor to consider (for organic chemistry alkanes, etc), is branching, which reduces the surface area available for van der Waals interactions.
And for alkenes, the cis isomer (having a greater polarity) has a higher boiling point than the trans isomer, but the cis isomer may (or may not) have a lower melting point than the trans isomer, because there is the additional factor of effectiveness of stacking, which relates to the Coloumb's law and strength of van der Waals interactions.
Medical science is complex, because human biology, human chemistry and human genetics are complex. So while Taurine (or any supplement, for that matter) certainly isn't a magic bullet nor even necessarily helpful (depending on your genetics and exact underlying medical condition, it may or may not be helpful); notwithstanding, self-education is your own responsibility (do your own online research to see if Taurine, or any other supplement for that matter, is worth your trying it out). At the same time, as the adage advises, while knowledge can be empowering, a little knowledge is a dangerous thing. So always proceed in life with sensible caution.
Decreased Myocardial Taurine Levels and Hypertaurinuria in a Kindred with Mitral-Valve Prolapse and Congestive Cardiomyopathy
Our study suggests that hypertaurinuria is associated with low levels of taurine in the myocardium, one type of the mitral-valve-prolapse syndrome, and a form of congestive cardiomyopathy. Hypertaurinuria may also account for the relatively rapid development of congestive cardiomyopathy in the two subjects with initially uncomplicated mitral-valve prolapse. It is also not clear whether the depressed myocardial taurine levels are etiologically related to the two heart diseases, whether all three disorders are coincidental genetic accidents, or whether the depressed myocardial taurine concentration is the cause of congestive cardiomyopathy alone and is unrelated to mitral-valve prolapse. The available evidence favors the hypothesis that all three problems are related.
Regardless of the extent of the possible interrelation, one additional point is evident: the syndrome of mitral-valve prolapse, with all its clinical and echocardiographic features, was not caused by mucinous transformation, scalloping of the mitral leaflets, or elongation of the chordae tendineae. Rather, a pathologic process in the papillary muscles seems to be the underlying cause â€” an interpretation that supports the view that mitral-valve prolapse is a syndrome with diverse causes.
Taurine (2-aminoethanesulfonic acid) is the most abundant free amino acid in the heart, accounting for more than half the total free amino acid pool. Circulating taurine derived from either dietary sources or from biosynthetically active tissues is taken up at various sites, particularly in cardiac and skeletal muscle. The rate of turnover of taurine in normal myocardium is extremely slow, with a half-life of approximately 15 days. Cardiac taurine levels are unchanged by a pyridoxine-deficient diet, fasting, or taurine loading; however, taurine concentrations rise in failing or hypertrophied myocardial tissue.
Loss of cardiac-muscle taurine has been demonstrated in left-ventricular tissue of anesthetized dogs in which ischemia was induced by occlusion of the coronary artery; in the absence of fibrosis, loss occurred as early as four hours after occlusion in one study and at 16 hours in another. In the family members in our study who were patients, however, there was no evidence of extramural or intramural narrowing of the coronary artery in the cardiac tissue in which myocardial taurine levels were depressed. Furthermore, there was no clinical evidence of ischemic heart disease in these patients.
On the other hand, studies in animals and one study of human myocardium at autopsy have both shown moderate to marked elevation of taurine levels in failing or hypertrophied hearts; this elevation was also present in the controls with cardiomyopathy in our study. However, family members with congestive cardiomyopathy had abnormally low levels of myocardial taurine in failing hearts. It therefore appears that at least some of these family members have an unusual combination of features: an absence of myocardial infarction in the presence of myocardial taurine levels that were abnormally low, particularly in comparison with levels found in other studies suggesting that myocardial taurine is elevated in congestive heart failure, perhaps as a compensatory positive inotropic mechanism.
Although a direct causal relation cannot yet be firmly established, it seems likely that in subjects described in this study, clinical and echocardiographic features of mitral-valve prolapse were produced by an early, localized cardiomyopathy in the papillary muscles that was associated with a depressed myocardial taurine concentration and eventual myocardial fibrosis. The congestive cardiomyopathy probably represents an extension of the local process to more or all of the remaining myocardium.
* Both the religious-inclined and the atheistic-inclined will no doubt seize upon such examples to egregiously claim rigorous support for each of their own Intelligent-Design-Creator-Creationism and Natural-Selection-Darwinism-Evolution beliefs respectively, but both would be equally inadequate, and would behoove a separate discussion for another day.
"Taurine, glutathione and bioenergetics" by Hansen SH, Grunnet N.
Biochemistry textbook presentations of bioenergetics and mitochondrial function normally focus on the chemiosmotic theory with introduction of the tricarboxylic acid cycle and the electron transport chain, the proton and electrical gradients and subsequent oxidative phosphorylation and ATP-production by ATP synthase. The compound glutathione (GSH) is often mentioned in relation to mitochondrial function, primarily for a role as redox scavenger. Here we argue that its role as redox pair with oxidised glutathione (GSSG) is pivotal with regard to controlling the electrical or redox gradient across the mitochondrial inner-membrane. The very high concentration of taurine in oxidative tissue has recently led to discussions on the role of taurine in the mitochondria, e.g. with taurine acting as a pH buffer in the mitochondrial matrix. A very important consequence of the slightly alkaline pH is the fact that the NADH/NAD(+) redox pair can be brought in redox equilibrium with the GSH redox pair GSH/GSSG.An additional consequence of having GSH as redox buffer is the fact that from the pH dependence of its redox potential, it becomes possible to explain that the mitochondrial membrane potential has been observed to be independent of the matrix pH. Finally a simplified model for mitochondrial oxidation is presented with introduction of GSH as redox buffer to stabilise the electrical gradient, and taurine as pH buffer stabilising the pH gradient, but simultaneously establishing the equilibrium between the NADH/NAD(+) redox pair and the redox buffer pair GSH/GSSG.
This will likely be my final post on Taurine (unless I've reason to update my views on it). As a concluding overview, the benefits of Taurine seem to far outweigh the cons, because Taurine appears to have a wide-range of health and medical benefits, and medical studies have shown no toxicity risk even from much higher daily dosages of Taurine than what you can get from daily supplementation. And you'll be glad to know Taurine is really cheap, at least compared to other anti-oxidants such as CoQ10 (especially the more expensive reduced Ubiquinol secondary alcohol form, rather than the cheaper oxidized Ubiquinone ketone form), and Glutathione (in which many people suffer from a genetic deficiency of, caused by rather common MTHFR or MethylFolate Reductase gene mutations and polymorphisms). So yeah, Taurine is really cheap, and works synergistically with other anti-oxidants such as vitamin C, CoQ10, Glutathione, etc.
Do your own research on Taurine, and decide for yourself if you want to give it a try. Wide-ranging benefits, with little or no toxicity risk (Taurine is naturally occurring in foods, and is the most abundant amino acid, technically amino-sulfonic acid, found in human body tissues due to it's important metabolic roles). And supplementation is really cheap, too. And if you (or any family or friend) are at risk of more serious (potentially fatal) heart diseases, including mitral valve prolapse, mitral valve regurgitation, congestive heart failure, etc, you'll be desperate to try anything that might help, and cheap Taurine has been medically shown to be safe and non-toxic. Enough said.
Benefits of Taurine :
Hundreds of thousands of Americans poisoned with permanent brain damage due to high levels of lead in city's drinking water gone undetected for decades.
Did you know... the Mad Hatter character from "Alice In Wonderland" is based on the tragic real-life cases of millions of people gone mad (ie. permanent brain damage) from wearing and/or producing hats, poisoned by mercury used in the manufacturing process of the hats, gone undiagnosed for several centuries!
A BedokFunland JC H2 Chemistry Question :
1. Explain why or how heavy metals cause toxicity in the human body (there are several modalities, use any modality you're familiar with, and/or from the H2 Chemistry and/or H2 Biology syllabus). Include relevant equations and/or diagrams in your answer.
2. State the medical treatment for heavy metal poisoning, eg. lead poisoning, explain why or how this medical treatment works. Include relevant equations and/or diagrams in your answer.
The thermal decomposition of ammonium sulfate(VI) generates 3 gases as the only products. Draw out the full curved-arrow reaction mechanisms for both the forward and backward reactions. Explain how the changes in enthalpy and entropy pull the reaction into opposite directions (specify the directions), and concordantly, explain how temperature therefore controls the position of equilibrium as predicted by the two relevant Gibbs free energy formulae : one relating Gibbs free energy change to enthalpy and entropy changes, the other relating Gibbs free energy change to equilibrium.
It can be observed that iron structures rust more rapidly when exposed to sea-spray, ie. iron rusts more rapidly when in contact with salt water, compared to pure water. If you ask around or look this up on the internet, the 'answers' you'll find simply say, "that's because salt water is a better conductor of electricity compared to pure water".
While the statement states the obvious regarding electrical conductivity, it does NOT explain the faster rate of rusting, which principally involves the oxidation of iron and the reduction of oxygen gas (occurring in several steps, involving several different redox equations; and if you research deeper beyond A levels, involves acid-base equilibria, solubility equilibria, coordination complex equilibria, and dehydration equilibria as well).
Fact is, it's a safe bet that almost all of the people on the internet (however well-intended they may be, bless their souls) who gave the abovementioned 'answer' on the internet, that "salt water is a better conductor of electricity compared to pure water", don't actually correctly understand how salt water speeds up rusting. Most 'answers' on the internet give no further elaboration (because they don't actually know the answer and are 'smoking' their way through), while a few imply (erroneously!) either that the salt water itself can help to carry the electrons (from the iron being oxidized to the oxygen gas being reduced), or suggest (erroneously!) that the salt ions present eg. Na+(aq) and Cl-(aq), help to 'temporarily accept and carry' the electrons (from the iron being oxidized to the oxygen gas being reduced), machiam or as if these ions were a chemical catalyst.
Neither of these ideas are correct, since salt water conducts electricity in the form of mobile ions rather than mobile electrons; and based on redox potentials (even considering non-standard molarities in sea water), neither Na+(aq) or Cl-(aq) (or for that matter, almost all of the other ions present in sea water) can be reduced in aqueous conditions to 'temporarily accept and carry' the electrons (from the iron being oxidized to the oxygen gas being reduced).
My BedokFunland JC H2 Chemistry Challenge for you is : Explain the correct mechanism by which salt water speeds up the rusting of iron.
Remember, just writing, "that's because salt water is a better conductor of electricity compared to pure water" in the A level exams should Cambridge ask you this question, will only cause the Cambridge marker to roll eyes and expose your epic-fail attempt at 'smoking' (which is hazardous to your health and grades), and earn you a big fat zero mark.
As with all my BedokFunland JC questions and challenges, I won't reveal the correct answer here. My BedokFunland JC students can ask me during tuition, and all other students can go ask your school teacher or private tutor. Usually I would say, "you can post your attempted answer here, and I'll tell you if you got it correct", but in this case, I will instead say, if you're sure you know the correct answer, DON'T post it here and ruin the fun for others! *insert sadistic laughter*
It took only a few seconds for 2 drops of dimethylmercury which accidentally fell on her latext gloved hand to be absorbed into her skin, but these 2 drops of dimethylmercury took its time to kill her slowly and painfully over 11 months before she finally died.
Dimethylmercury is formed by treating sodium amalgam with methyl halides :
Hg + 2 Na + 2 CH3I â†’ Hg(CH3)2 + 2 NaI
Dimethylmercury can also be obtained by alkylation of mercuric chloride with methyllithium :
HgCl2 + 2 LiCH3 â†’ Hg(CH3)2 + 2 LiCl
A couple of BedokFunland JC Original H2 Chemistry Questions :
Q1. For the two synthesis methods described above, one involves an ionic mechanism, the other a free radical mechanism. Deduce, with reasons, which is which. Draw out the full curved-arrow electron-flow reaction mechanisms for both synthesis methods. In your mechanism structures (for both reactants and products, for both synthesis methods), label the oxidation states for all the Hg and C atoms.
Q2. Write out the full electron configuration of Hg, Hg+ and Hg2+. Mercury is a d-block metal, but is it a transition metal? Explain your answer. Suggest the bond angles and hybridized orbitals (of both the C and Hg atoms) involved in forming each sigma bond in dimethylmercury, and explain your answer.
Q3. "Dimethylmercury is metabolized after several days to methylmercury. Methylmercury crosses the bloodâ€“brain barrier easily owing to formation of a complex with cysteine." There are two possible positional isomers (both of which exhibit enantiomerism) for this complex, in which the Hg atom can be either coordinated to the S or to the O atom. Draw the structure of both isomeric complexes (labeling chiral atoms with an asterisk). Suggest which isomer crosses the bloodâ€“brain barrier more readily, and explain your answer.