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Hi, A similar reaction appeared in 2022 H2 Chemistry exam papers. This is known as the Michael reaction. The bottom reaction is an example of mixed Aldol condensation. This reaction was of interest to Cambridge examiner in 2022. This reaction is known as the Cannizzaro reaction. If I am not wrong, some NUS undergraduates only learned this reaction in NUS Year 4. Now Cambridge examiners are setting many undergraduate organic chemistry reactions, possibly with induction of new and smarter Cambridge and SEAB examiners who are possibly top PhD students in the top 10 universities. So students need to be well prepared for Chemistry exams.
Hi, Some novel molecules appeared in 2022 H2 Chemistry Paper 1 and 2 exam papers. Here is an aldol: Here is an enolate ion: Here are allotropes of carbon. Graphene appeared in 2022 H2 Chemistry Paper 2. This elderly experienced Cambridge examiner adores this copper(II) complex: Selenium compounds appeared in 2022 H2 Chemistry Paper 2. Here is an acid that is analogous to sulfuric acid, since sulfur and selenium are in Group 16. This is a thiol. A thioacetic acid appeared in 2022 H2 Chemistry Paper 1.
Hi, the Cambridge examiners were thinking about these related reactions which appeared in 2022 H2 Chemistry exam papers. Here is a link to a powerpoint file of keto esters and their related reactions: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwj_weez0OH_AhVQxzgGHVXrD-cQFnoECA0QAQ&url=https%3A%2F%2Fwww.vanderbilt.edu%2FAnS%2FChemistry%2FRizzo%2FChem220b%2FCh21.ppt&usg=AOvVaw1p-eFo_Nf13I8fdqclwmgT&opi=89978449
Hi, diazonium salt appeared in 2022 Cambridge-Singapore H2 Chemistry papers. So here are some related reactions of diazonium salts. Cambridge examiners were examining carboxylic acid derivatives (keto esters) and carbonyl condensation reactions in Cambridge-Singapore H2 Chemistry exam papers in 2022. Here is a related Mannich reaction.
Hi. Aldol condensation reaction had been appearing in Cambridge papers and JC H2 Chemistry prelim papers in the recent years. All thanks to the professor who created this diagram on internet, students who are hungry for success may learn this mechanism. Carbonyl chemistry is one of the most complex chapters in undergraduate chemistry course and now such questions appear in A level Chemistry papers.
In organic chemistry , the Diels–Alder reaction is a chemical reaction between a conjugated diene and a substituted alkene to form a substituted cyclohexene derivative. Draw the formula of the product C when the following diene and cycloalkene undergo Diels Alder reaction. Also, outline the mechanism of this pericyclic Diels-Alder reaction.
Cyclopropane rings are precursors in synthesizing certain pharmaceutical medicine and substituted cyclopropane is also involved in biochemical pathways (biosynthesis of certain biomolecules) of bacteria. The following reaction shows part of the synthesis for a cyclopropane compound. The above reaction involves a negatively-charge organic intermediate which is relatively stabilised, which eventually forms the cyclopropane compound. (a) Suggest the reaction types for steps 1 and 2 and draw the structural formula of the organic intermediate. (b) How is the intermediate stabilised? a Propose a mechanism for the above reaction. (c) Which has more conformational stability, cyclopropane or cyclohexane? Explain briefly your answer.
A nucleophilic aromatic substitution is a substitution reaction in organic chemistry in which the nucleophile displaces a good leaving group, such as a halide, on an aromatic ring. This is an unusual reaction for H2 Chemistry students because electrophilic aromatic substitution is usually encountered for arenes. An example: SNAr mechanism: In the mechanism, electron withdrawing groups activate the ring towards nucleophilic attack, for example if there are nitro functional groups positioned ortho or para to the halide leaving group. Explain which mechanism will yield the fastest rate given that the nucleophile is methoxide ion, CH3O-, and the each of the substrates are given below. Draw the organic products that are formed.
In the chapter of electrochemistry, the Nernst equation is in the grey area of the syllabus. So let us look briefly at what is the Nernst equation. Understanding the Nernst Equation The Nernst equation finds the cell potential of a reaction, or how much "power" a reaction will have at any given moment. You can use the equation to find out how much juice is in your battery. Below is the general formula for the Nernst equation. You'll need to refer to it again when we perform our sample calculations. You may be wondering what all those letters in the equation mean. To decipher them, take a look at the key below: E : refers to the cell potential, or the amount of voltage, the reaction will have under set conditions. Eo : refers to the cell potential, or voltage, the reaction will have under set-standard conditions. R : refers to the ideal gas constant, which is 8.314 J/mol-K. T : refers to the temperature in Kelvins (K); room temperature equals
Free-radical polymerization is a method of polymerization by which a polymer forms by the successive addition of free-radical building blocks. Free radicals can be formed by a number of different mechanisms, usually involving separate initiator molecules. Following its generation, the initiating free radical adds monomer units, thereby growing the polymer chain. Illustrate the first two steps of the mechanism when the monomer is ethene and the initiator molecule is di cumyl peroxide.
Pinacol Rearrangement The pinacol rearrangement was the first molecular rearrangement identified as such by early chemists. The defining example of a pinacol rearrangement is shown in the following diagram. As shown in the mechanism, from the initial diol, there is a shift of a methyl group to an adjacent carbon, and a carbonyl group is produced in the final step of the mechanism. Predict the product when the following molecule undergoes pinacol rearrangement:
The E1 mechanism involves the elimination of a molecule HBr from the alkyl halide to form an alkene. It is a first order reaction. The mechanism is as shown: Suggest how the kinetics of the reaction is affected as a stronger base is used, such as the ethoxide ion, CH3CH2O-, instead of hydroxide ion. Why might carbocation rearrangement sometimes occur in E1 reaction?
Protecting groups in organic chemistry A protecting group or protective group is introduced into a molecule by chemical modification of a functional group to obtain chemoselectivity in a subsequent chemical reaction. It plays an important role in multistep organic synthesis. In many preparations of delicate organic compounds, some specific parts of their molecules cannot survive the required reagents or chemical environments. Then, these parts, or groups, must be protected. For example, lithium aluminium hydride is a highly reactive but useful reagent capable of reducing esters to alcohols. It will always react with carbonyl groups, and this cannot be discouraged by any means. When a reduction of an ester is required in the presence of a carbonyl, the attack of the hydride on the carbonyl has to be prevented. For example, the carbonyl is converted into an acetal, which does not react with hydrides. The acetal is then called a protecting group for the carbonyl. After the step in
Hi , here are some summary notes which I have found from internet for use during home based learning. They are in a zipped file. So just download from this link below and unzip the files and you are ready to use the notes. Keep safe!! https://drive.google.com/open?id=176oOzxSs6PYcZPwLbpzeXUAJHM5aQXq1 Summary notes found from internet: https://drive.google.com/open?id=1NE8M7SO9fxGMXdzH_6I2nJbIj3XK5Gz9 https://drive.google.com/open?id=1pm8Qnv61KvWiZ06J5xU3O4doCv-x6JpX https://drive.google.com/open?id=1B7yOWIlnU4m3QSCDh5P6BPCU0NCHhJlP https://drive.google.com/file/d/1aIi2VtWrFnYhrEEjZRk4nsAOOv4cf7OJ/view?usp=sharing Best regards, Mr Chong P / S online 1-1 interactive and live online tuition is available from me. Completely Compiled Chemistry for Singapore JC H2 syllabus by Chong56 on Scribd
Download file here : https://drive.google.com/open?id=1LqrgvNkw2BxqvNt7EbcYIP-sPU4V5UwH Question : An organic compound X contains by mass, 63.2% carbon, 8.7% hydrogen, and 28.1% oxygen. On treatment with sodium hydrogencarbonate solution, it liberates carbon dioxide. It also undergoes an addition reaction with bromine in a 1:1 molar ratio whereby 1.50 g of the compound reacts with 2.11 g of bromine. (i) Calculate the empirical formula of X . (ii) Calculate the relative molecular mass of X . (iii) Determine the molecular formula of X . Answer : Molecular formula of X is C 6 H 10 O 2 Bonus question : 25.0 cm 3 of a solution containing sodium hydroxide and sodium carbonate required 21.05 cm 3 of 1 mol dm -3 HCl with phenolphthalein as indicator and a further 6.80 cm 3 of the same acid with methyl orange as indicator. Calculate the molar concentration of each compound in the solution. Ans: conc of sodium carbonate = 0.272 mol dm-3 conc of sodium hydroxide = 0.
Hi all, Some heterocyclic organic compounds containing O, N or S atoms have appeared in 2019 H2 Chemistry Prelim Papers. So you may wish to read up on lactones, pyrroles or furans only if you have time. You may search for "lactones" or "furans" or "pyrrole" in wikipedia. All the best for your examinations!! RI and TJC have set similar questions to 2019 A level chemistry exam papers. So it maybe worthwhile to look at their prelim papers for this year once they are available. Signing off, :) Mr Chong