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Originally posted by Flying grenade:
why R- and H- more strong and unstable than OH- ?
If you still can't figure out, go ask your school teacher or private tutor. Edart sterces.
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Originally posted by Flying grenade:
y
Because he's not wrong.If you still can't figure out, go ask your school teacher or private tutor. Edart sterces.
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trans
https://www.dropbox.com/s/oabzqc9aqa0y8qp/20161006_171942.jpg?dl=0
https://www.dropbox.com/s/2dxoa52rjsq0qz2/20161006_172012.jpg?dl=0
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eh 2 carboxylic acids undergo dehydration to form acid anhydride uh?
can i name this rxn condensation?
https://www.dropbox.com/s/52omev0kniqpmfz/20161006_175926.jpg?dl=0
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ooh just realised nitrobenzene cannot act as a base as N atom does not have a lp of e-
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Originally posted by Flying grenade:
eh 2 carboxylic acids undergo dehydration to form acid anhydride uh?
can i name this rxn condensation?
https://www.dropbox.com/s/52omev0kniqpmfz/20161006_175926.jpg?dl=0
Obviously. Obviously. -
Originally posted by Flying grenade:
ooh just realised nitrobenzene cannot act as a base as N atom does not have a lp of e-
Obviously. -
Originally posted by UltimaOnline:
Because he's not wrong.If you still can't figure out, go ask your school teacher or private tutor. Edart sterces.
circular reasoning
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Originally posted by UltimaOnline:
Obviously. Obviously.thanks
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Originally posted by Flying grenade:
circular reasoning
Suitable for coconaden pple like u. U still stubbornly keep reading ur books and keep asking qns about them, instead of doing Prelim papers and asking qns from there instead, it'll be reflected in ur final A level results. For A grade students, the studying books stage is long over, the prelim paper practicing stage is now. -
Hi, may I ask A Level 2012 P3 q5 c?
For this structure elucidation question,I derived that L has no aldehyde/ketone/alcohol/COOH groups.
M has to be an acidic salt, and alkene is present in M.
I have problems deducing M, assuming my L is right.
L is an acid anhydride right? But my L seems to be "cyclic" and I don't know how to add NH3 to it. From the question, it seems that the whole NH3 is added. How can NH3 be added when nothing is removed??
Some of my thinking: L is similar to acyl chloride, so reaction may be similar. But to form salt...?
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Originally posted by supercat:
Hi, may I ask A Level 2012 P3 q5 c?
For this structure elucidation question,I derived that L has no aldehyde/ketone/alcohol/COOH groups.
M has to be an acidic salt, and alkene is present in M.
I have problems deducing M, assuming my L is right.
L is an acid anhydride right? But my L seems to be "cyclic" and I don't know how to add NH3 to it. From the question, it seems that the whole NH3 is added. How can NH3 be added when nothing is removed??
Some of my thinking: L is similar to acyl chloride, so reaction may be similar. But to form salt...?
Correct. Carboxylic acid anhydrides are electrophiles similar to acyl halides.Draw out (if you're not familiar, you can google it online and familiarize yourself with it, it's compulsory for H3 syllabus, and very useful / good-to-know for H2 syllabus) the addition-elimination mechanism for the nucleophilic acyl substitution, together with a subsequent Bronsted-Lowry acid-base proton transfer.
Only by drawing out the mechanism of this reaction for yourself, will you be able to truly, properly and correctly understand this reaction.
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The order of reaction wrt a given reactant is the power to which the reactant's concentration is raised to in the experimentally determined rate equation
the Orders of reactions are experimentally determined quantities
they may or may not be equivalent to the stoichiometric coefficients of the reactants in the balanced chemical equation
what are the significance/implication/meaning when the orders of reactions are the Same as the stoichiometric coefficients of the reactants in the balanced chemical equation?
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https://en.m.wikipedia.org/wiki/Order_of_reaction
The overall reaction order is the sum x + y + .... For many reactions, the reaction orders are not equal to the stoichiometric coefficients.
Elementary (single-step) reactions do have reaction orders equal to the stoichiometric coefficients for each reactant. The overall reaction order, i.e. the sum of stoichiometric coefficients of reactants, is always equal to the molecularity of the elementary reaction.Complex (multi-step) reactions may or may not have reaction orders equal to their stoichiometric coefficients
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Originally posted by Flying grenade:
The order of reaction wrt a given reactant is the power to which the reactant's concentration is raised to in the experimentally determined rate equation
the Orders of reactions are experimentally determined quantities
they may or may not be equivalent to the stoichiometric coefficients of the reactants in the balanced chemical equation
what are the significance/implication/meaning when the orders of reactions are the Same as the stoichiometric coefficients of the reactants in the balanced chemical equation?
Hint : draw out the mechanism for such a reaction, then the significance becomes clear.
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An elementary reaction is a chemical reactionin which one or more chemical species react directly to form products in a single reaction step and with a single transition state. In practice, a reaction is assumed to be elementary if no reaction intermediates have been detected or need to be postulated to describe the reaction on a molecular scale.[1]An apparently elementary reaction may be in fact a stepwise reaction, i.e. a complicated sequence of chemical reactions, with reaction intermediates of variable lifetimes.
In a unimolecular elementary reaction, amolecule A dissociates or isomerises to form the products(s)
https://en.m.wikipedia.org/wiki/Elementary_reaction
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BedokFunland JC H2 Chemistry Kinetics + Organic Chem Challenge :
For the Singapore 2015 A Levels H2 Chemistry P3 Q4d, draw the full mechanism (including the 2 relevant resonance contributors) to fully explain the kinetics of the reaction.
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Originally posted by UltimaOnline:
Correct. Carboxylic acid anhydrides are electrophiles similar to acyl halides.Draw out (if you're not familiar, you can google it online and familiarize yourself with it, it's compulsory for H3 syllabus, and very useful / good-to-know for H2 syllabus) the addition-elimination mechanism for the nucleophilic acyl substitution, together with a subsequent Bronsted-Lowry acid-base proton transfer.
Only by drawing out the mechanism of this reaction for yourself, will you be able to truly, properly and correctly understand this reaction.
Is it like this? http://imgur.com/mdIfXtV
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Originally posted by supercat:
Is it like this? http://imgur.com/mdIfXtV
Wrong. You need to reform the acyl group (ie. lone pair on negative formal charged O atom, shifts down to form a pi bond pair) and eliminate the RO leaving group as alkoxide RO-, before proton transfer occurs. -
why larger size is a weaker base? less electronegative, lp of e- more readily donated and available , wouldn't it more readily accept proton? larger atomic radius too
i know larger size e- cloud more diffused, less effective overlap when forming covalent bonds, result in weaker covalent bonds
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Originally posted by Flying grenade:
why larger size is a weaker base? less electronegative, lp of e- more readily donated and available , wouldn't it more readily accept proton?
i know larger size e- cloud more diffused, less effective overlap when forming covalent bonds, result in weaker covalent bonds
I won't spoonfeed you (or anyone) on the forum with the answers. Go figure it out for yourself, and/or go ask your school teacher or private tutor.What you've described is about nucleophilicity, but Bronsted-Lowry basicity is a different matter altogether. A stronger nucleophile may or may not be a stronger Bronsted-Lowry base, case-by-case basis. Similarly, for ligand strength (which is also a separate matter from ligand field strength).
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i think related to charge density and polarisability of e- cloud
a large atomic size affects polarizability by allowing the negative charge on the conjugate base to be distributed better, hence the acid is overall more acidic.
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larger ion allows dispersal of charge over a larger area less reactive, less basic , more stable
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Originally posted by UltimaOnline:
Wrong. You need to reform the acyl group (ie. lone pair on negative formal charged O atom, shifts down to form a pi bond pair) and eliminate the RO leaving group as alkoxide RO-, before proton transfer occurs.http://imgur.com/fy4jZXf
Like this??
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Originally posted by supercat:
http://imgur.com/fy4jZXf
Like this??
