June 2012
45 posts
5 tags
Question on Grignard Reagent
What is the name of the ester, having molecular formula C2H4O2, which on treatment with MeMgI, followed by hydrolysis produces acetaldehyde as the product?
Answer:
Methyl Formate
4 tags
The Scent of Rain
The scent of rain is one of the things that comes to our mind when we think about a rainy day. The smell is so intense in air that you can not miss it. Geosmin is responsible for this strong scent that is present in air when rain falls after a hot or dry weather.
Geosmin is produced by several class of microbes especially the Streptomyces. Geosmin is released when these microbes die. Geosmin...
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Question on Grignard Reagent
Ethyl acetate is treated with double molar quantity of C2H5MgBr and the reaction mixture is hydrolysed with H2O to a produce a product “P”. What is the name of “P”?
Answer:
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Hunsdiecker Reaction
Reaction: Hunsdiecker Reaction
Reagent: Br2/CCl4
Use in Chemistry: Conversion of Silver salts of carboxylic acids to alkyl halides
Reaction Examples:
Reaction Mechanism:
The widely believed mechanism involves the Silver salt of the carboxylic acid reacting with bromine to form acyl hypobromite which undergoes homolytic bond cleavage to produce bromine radical and a carboxylate radical. This...
2 tags
“Science is a great game. It is inspiring and refreshing. The playing field is...”
– Isidor Isaac Rabi - Physicist and Nobel Prize winner.
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Question on Sulphonation
What will the ascending order of the rate of sulphonation of the following molecules?
Answer:
Activating groups increase the rate of electrophilic aromatic substitution while deactivating groups decrease the rate of such reaction.
The ascending order of the rate of sulphonation of the given compounds will be (IV) < (II) < (I) < (III)
4 tags
Question on Nitration
Nitrobenzone can be prepared from benzene by using a mixture of conc. HNO3 and conc. H2SO4. In the nitrating mixture, what is the role of H2SO4?
Answer:
H2SO4 makes HNO3 act as a base and produce nitronium ion (NO2+).
3 tags
Question on Chemical Kinetics
The time required for 99.9% completion of the first order reaction is “x” times to that of its half life time. What is the value of “x”?
Answer:
10
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Question on Molecular Formula
A compound A crystallizes in a hexagonal close packing system. If the compound is made of X and Y in which X occupies all the lattice position of hcp layers and Y occupies two third of the octahedral voids, what will the formula of A be?
Answer:
X3Y2
4 tags
Question on Freezing Point
What will happen to the freezing point of an aqueous solution of potassium iodide when mercuric iodide is added to it?
Answer:
Addition of mercuric iodide to an aqueous solution of potassium iodide will form K2[HgI4] according to the following equation.
2KI + HgI2 = K2[HgI4]
So, the addition of mercuric iodide will decrease the number of ions in the solution. This will make the depression...
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Hydroxycitric Acid
Hydroxycitric acid (HCA) is a derivative of citric acid and is found in variety of tropical plants. It is found in Garcinia Indica commonly known as kokum and is used in Indian & Thai food as a flavoring agent.
Earlier experiments with HCA on mice showed that when mice were administered with HCA along with their food, it made them eat less.
If our food contains large amounts of...
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Base and Nucleophile
A negatively charged species can act both as a base and also as a nucleophile. When an alkyl halide reacts with a negatively charged species there are two possible outcomes; elimination and substitution. If the outcome is elimination the negatively charged species has played the role of a base and if the outcome is substitution then the negatively charged species has acted as a nucleophile.
If we...
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Question on Basic Strength
Is a 0.01 N solution of Ca(OH)2 more basic than a 0.01 M solution of Ca(OH)2? Why?
Answer:
No. 0.01 N solution of Ca(OH)2 is 0.005 M. SO, it will produce 0.01 M hydroxide ions while 0.01 M solution will produce 0.02 M hydroxide ions.
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Question on Chemical Equilibrium
If at 100°C, the vapour density of N2O4 is 26.8, what is the degree of dissociation of N2O4 at this temperature?
Answer:
0.72
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Question on Stoichiometry
If 3.68 g of a mixture of CaCO3 and MgCO3 when heated strongly leave 1.92 g of a white residue what is the percentage composition of the mixture?
Answer:
CaCO3 = 57.75% and MgCO3 = 42.25%
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Aspartame
Aspartame is an artificial sweetener. It is used as a substitute for sugar in food and some beverages. It is the methyl ester of the dipeptide of L-aspartic acid and L-phenyl alanine. Both L-aspartic acid and L-phenylalanine are natural amino acids. It is said that aspartame is almost 200 times sweeter than sugar. This property allows us to have the same amount of sweetness as sugar but will a...
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Question on Glucose
How many molecules of phenyl hydrazine reacts with one molecule of glucose to produce glucosazone?
Answer:
3 molecules
4 tags
Question on Molecular Structure
How many sigma bonds (a), pi bonds (b) and lone pair of electrons (c) respectively are present in the enolic form of acetone?
Answer:
It has 9 sigma bonds, 1 pi bond and 2 lone pair of electrons.
3 tags
Question on Precipitation
7-Bromo-cycloheptatriene gives a precipitate of AgBr with AgNO3. Why?
Answer:
It is because, after losing the bromide ion the remaining 7 membered ring becomes aromatic and hence becomes more stable.
3 tags
