General Organic Chemistry Flashcards
What is the general formula of amines ?
R- NH2
What is the general formula of aldehyde ?
R- CHO
What is the general formula of ketones?
R-COR
What is the general formula of esters ?
RCOOR
What is the general hybridisation of a carbonation ?
sp²(often)/ sp (less often)
Order of migratory aptitude ?
Hydride > Phenide > 3 degree C> 2 degree C >1 degree > Methyde.
Ring expansion
4 membered ring stabilises to 5 and 5 membered ring stabilises to 6. Ring expansion is favoured over hydride shift.
Does any rearrangement happen in carbanion ?
Nope.
What is the order of carbon radicle that has to be memorised ?
CF₃>CH₃
Order of -I effect strength
R₃N+>NO₂>CN>SO₃H>CHO>CO>COOH>F>Cl>Br>I>OH>OR>NH₂>Benzene> H
Order of +I effect strength
-O->-COO->3 alkyl>2 alkyl>1 alkyl> CH₃> H
Stability of carbocation
CH=CH C+H2 and C₆H₅C+H2>3⁰>2⁰>1⁰>CH₃+
Stability of carbanion
C- H₃>1⁰>2⁰>3⁰
-I effect if due to electron ? groups
Electron attraction groups
+I effect is due to electron ? groups
Electron repelling groups
Mesmeric effect is ?
π electron shift in conjugate system
Hyper conjugation is ?
Electron release by alkyl group attached to unsaturated group
When is markoniknov’s rule followed ?
When there is addition of HX to unsymmetrical alkenes
Intermediates are ?
Intermediates are carbocations which may undergo 1,2 hydride or 1,2 alkyl shift to attain more stability
Under what conditions is addition reaction against markoniknov’s rule ?
In presence of peroxides , addition is against markoniknov’s rule
What’s the order rate of a SN2 reaction
Second order rate
What the effect of nucleophiles on SN2 reaction
Stronger nucleophiles causes faster rate
SN2 reactions are favoured by ? solvents
Aprotic solvents
What’s the strongest organic acid ?
Sulphunic Acid ( it’s conjugate base is stabilise by 3 resonating structures )
Strongest organic base
Guanidine ( it’s conjugate acid is stablized by 3 equidistant resonating structures )
Order of strength of 3 electron displacement effect
Mesmeric effect > Hyperconjugation > Inductive ( for halogens, inductive dominates )
List of some nucleophiles ( electron rich )
e-, all Lewis base, conjugate base of bronsted acid , carbanion , all pi bonds.
List of some electrophile ( electron loving )
H+ All Lewis acid ium ions Carbocation Acylium
Formal charge F=?
F=Z-S/2-U
;Z-Group Number
S-Number of shared electrons
U-Number of unshared electrons
In resonating structures , are all C-H bonds of equal length ?
Yes
Rules of writing resonating structures
We are only allowed to move electrons and lone pairs. Energy of actual molecule is lower than its resonating structures. Equivalent resonating structures make equal contribution to resonance hybrid.
What are the characteristics of a stable resonating structure
Structure having filled octets for second row elements.
Structures having minimum number of formal charges and minimum number of bonds.
Negative charge on most electronegative atom.
Minimal charge separation keeping the formal charges closer together.
Which type of conjugation is called Hyperconjugation ?
When σ electrons of a CH bond are in conjugation with an adjacent π bond, such type of conjugation is called Hyperconjugation.
Condition for Hyperconjugation
The presence of α hydrogen at an alkene , alkyl carbocation , alkyl free radical , or a phenyl group is the main condition for Hyperconjugation
For alkenes , number of resonating structures =?
Number of resonating structures = Number of α hydrogen + 1
What’s Baker Nathan Effect
Hyperconjugation dominates inductive effect.
When is cis isomer more stable than trans isomer
Cis isomer is more stable than trans isomer when number of constituent atoms of the ring is less than 11
When is trans isomer more stable than cis isomer
When the ring contains more than 11 atoms
Which has a greater +I effect D or H?
+I effect of D is more than H
When does maximum overlap between the p orbitals of a π occur ?
When the axes of a p orbitals are exactly parallel.
When is an antibonding molecular orbital formed ?
An antibonding molecular orbital is formed when orbitals of opposite phase sign overlap. An antibonding orbital has a higher energy than a binding orbital.
4 categories of organic reactions
Substitution reactions.
Addition reactions.
Elimination reactions.
Rearrangement.
Substitution reactions are characteristic reactions of what kind of compounds ?
Saturated compounds such as alkenes and alkyl halides and aromatic compounds ( even though they are saturated ).
Addition reactions are characteristic reactions of what kind of compounds ?
Compounds with multiple bonds like Ethene. In addition reactions , all parts of the adding reagent appear in the products; two molecules become one.
Bronsted Lowry Theory of Acids and Bases
According to bronsted Lowry theory , Acids donate( or lose) a proton Bases accept ( or remove ) a proton.
Lewis definition of Acids and Bases
According to Lewis ,
Acids are electron pair acceptors.
Bases are electron pair donors.
Define vinylic halides
Compounds in which an halogen atom is bonded to a sp2 hybridised carbon are called vinylic halides.
Compound CH2=CH-Cl is commonly called ? And group CH2=CH- is commonly called ?
CH2=CH-Cl is Vinyl Chloride
CH2=CH- is vinyl group
Define Pheyl Halide
Phenyl halides are compounds in which a halogen is attached to a benzene ring.
Common name for trichloromethane (CHCl3)
Chloroform
General Nucleophilic Substitution Reaction
Nu+ R-X---->R-Nu+ X- ; Nu= Nucleophile R-X= Alkyl Halide( Substrate) X- = Halide ion
In Nucleophilic Substitution reaction , C- Halogen bond of the substrate undergoes heterolysis or homolysis ?
Heterolysis
Define Nucleophile
A Nucleophile is any negative ion or neutral molecule that has at least one unshared electron pair
General reaction of Nucleophilic Substitution of an alkyl halide by hydroxide ion
H-O(-) + R-X—->H-O-R + X(-)
General reaction for Nucleophilic substitution of an Alkyl Halide by water
H-O-H + R-X ----> H-O(+)-R-R + X(-)
;
H-O(+)-R = Alkyloxonium ion
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RProminent characteristic of a good leaving group
A good LG is a substrate that can leave as a relatively stable , weakly basic molecule or ion
Expand SN2
Substitution , Nucleophilic , bimolecular
A sample SN2 reaction with HO(-) and CH3Cl as reactant
HO(-) + CH3Cl—->CH3OH + Cl
How many steps does the Hughes Ingold mechanism for the SN2 reaction involve ?
1
What happens in the transition state of a SN2 reaction ?
In the transition state , both the Nucleophile and leaving group are partially bonded to the carbon atom undergoing substitution.
Define exergonic reaction
A reaction that proceeds with a negative free energy change is said to be exergonic.
Define endergonic reaction
A reaction that proceeds with a positive free energy change is called endergonic reaction.
Define free energy change of a reaction ΔG
The difference in free energy between the reactant and products is called the free energy change of the reaction
Expand SN1
Substitution , Nucleophilic and Unimolecular
Write a balanced SN1 reaction with (CH3)3CCl and H20 as reactants
(CH3)3CCl+2H20—->(CH3)3COH + H30+ Cl-
Define solvolysis
A solvolysis reaction is a Nucleophilic substitution reaction in which Nucleophile is a molecule of solvent.
4 factors that affect the rate of SN1 and SN2 reactions
Structure of substrate
Concentration and reactivity of the Nucleophile ( for bimolecular reactions only )
The effect of solvent
Nature of leaving group
2 types of solvents
Polar protic solvent
Polar aprotic solvent
Define polar protic solvent
Solvent which has hydrogen atom attached to a strongly electronegative element an hence forms a hydrogen bond to Nucleophile.
