Featured Post

A Level H2 /H1 Chemistry tuition and notes by ex-JC teacher

Reach your full potential with A Level H2 / H1 Chemistry tuition by ex-JC teacher   Why struggle in your chemistry studies? Do you need a grade boost? Do you want to do well for tests and exams?   You’ve come to the right place! My personalized and customised A level H2 /H1 Chemistry tuition is now available in 2024. I was an ex-JC tutor, graduated with a NUS Honours degree in Pure Chemistry, along with years of solid experience. I also graduated with a diploma in education from NTU - NIE. I was the top student in a secondary school, achieved 5 distinctions in A levels in a top junior college, and I was in Dean's list in NUS.   1-1 individual tuition service is provided, with value added services to improve the students' grades. Individual attention to the student and customised tuition are given.Customised feedback with motivation tips are provided for the student. Ad-hoc tuition with topical revision is also available. My offer to you :

Important Michael reaction and other related reactions

     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.

Pauling's electronegativity table

 This appeared in 2022 H2 Chemistry Paper 3. Fluorine is the most electronegative element and is assigned a Pauli's value of 4.0

Novelties in 2022 H2 Chemistry Chemistry Papers 1 and 2

       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.      

Peroxides as catalysts in free radical addition and some interesting peroxides

Hi, these are some interesting peroxy organic acids and use of peroxide in catalysing free radical addition. These questions are related to 2022 H2 Chemistry papers set by Cambridge-Singapore examiners.    

Transition metals - Phenanthroline molecular structure 2023

 Hi, phenanthroline appeared in UK Cambridge A levels Chemistry exam papers in Nov 2022. So this maybe of interest to students who are interested in Transition metals and their ligands. Ligand structure: Is this compound optically active?

Chemical Bonding 2023

 Hi, please try drawing the dot and cross diagrams of - P2O5 - N2O5 - NOCl - NO - NO2 - C3O - C2O3 - C2O - N2O2 - N2O These molecules are related to 2022 H2 Chemistry Exam Papers Question. All the best!

Organic Chemistry - Azo dye formation

 Hi, diazonium salts appeared in 2022 H2 Chemistry Exam papers. So here is a related reaction of the diazonium salt, which is an azo dye formation. Azo dyes are used in the textile industry.

Ester reactions which are related to 2022 H2 Chemistry exam reactions

 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:

Organic Chemistry reactions which are related to 2022 Cambridge H2 Chemistry papers

   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.    

Important Aldol condensation 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.    

Important Claisen condensation

A similar reaction appeared in 2022 Cambridge papers.

Chemistry of aqueous solutions - Acid-base equilibrium questions

 Chemistry of aqueous solutions - Acid-base equilibrium structured questions (35 pages)

Carbonyl compounds Structured questions with answers

 Carbonyl compounds Structured questions with answers - more than 100 pages long.

Claisen Condensation

This reaction mechanism may be of interest to students because similar reactions have appeared in Cambridge exam papers last 2 years.                                   Et stands for an ethyl group.

#Wagner Meerwin reaction - alkyl group shift

  Grateful to the owner for creating this on internet.

Organic Chemistry - Hydride shift

      I found this slide from the internet. Grateful  for the owner who created this slide. 

Diels Alder reaction Part 3

   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.

Novel question on cyclopropane

  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.

Organic Chemistry - Diels Alder reaction Part 2

 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 Z when the following diene and cycloalkene undergo Diels Alder reaction. 

Organic Chemistry Question - Hoffmann rearrangement

    The Hofmann rearrangement is the organic reaction of a primary amide to a primary amine with one fewer carbon atom.     Draw the formula of the final product formed when the above molecule undergoes Hoffmann rearrangement followed by reaction with excess benzoyl chloride.

organic chemistry - nucleophilic aromatic substitution

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.

organic chemistry - synthesis problem

How do you convert butanoic acid to 2-pentanone in less than 6 steps? You may need to use a Grignard reagent. Grignard reagent has appeared in prelim papers before. Read about Grignard reagents on wikipedia.

H2 Chemistry Prelim Papers

2017 Singapore H2 Chemistry Prelim papers by Chong56 on Scribd

Physical Chemistry - Brief look at the Nernst equation

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

organic chemistry - radical polymerization

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.

organic chemistry - pinacol rearrangement

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:

organic chemistry - challenging nitrogen compounds questions

Download the file here:

organic chemistry - E1 elimination reaction

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?

Challenging Chemistry of Aqueous solutions - acid base equilibria questions

 Hi, there are 24 pages of challenging questions and solutions. Download file here: Sample :

organic chemistry - Protecting Groups

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.[1] 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

Good JC H2 Chemistry summary notes

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!! Summary notes found from internet:   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

Physical Chemistry - Stoichiometry Question

Download file here : 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.

Reaction of arene question

When benzene reacts with 5-chloropentanoyl chloride in the presence of a catalyst, AlCl 3 , a few products are obtained. Suggest a likely organic product A.

Trends from 2019 H2 Chemistry Prelim Papers

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