General organic chem qns Flashcards
What is homolytic fission?
Breaking of covalent bonds->each atom in the bond pair takes in 1 bonding electron
What is heterolytic fission?
Breaking of covalent bonds-> pair of bonding electrons goes to one atom
What is a free radical?
An atom or grp of atoms with an unpaired electron -> very reactive
What is carbocation?
Carbon species-> carries +ve charge
What is carboanion?
Carbon species-> carries -ve charge
What is electrophile? What do they react with? Examples?
Species poor in electrons + reacts with electron rich species + attack region of high electron density + H+, CH3+, BF3
What is nucleophile? What do they react with? Examples?
Species rich in electrons + reacts with electron poor species + attack region of low electron density + OH-, CN-, NH3
What is hybridisation?
process of combining atomic orbitals to form hybrid orbitals
What is constitutional isomerism? What are the types?
Substances with same molecular formula different structural formula -> chain + positional + functional grp
What is stereoisomerism? What are the types?
Substances with same molecular formula same structural formula different arrangement of their atoms in space -> enantiomerism + cis-trans (restriction of rotation of double bond or ring)
What is enantiomerism?
non-superimposable mirror images each mirror image is optically active able to rotate plane-polarised light if 2 enantiomers are in equal proportion mixture is a racemic mixture and optically inactive
What is an acid?
An acid is a proton donor a weak acid dissociates partially in water
What makes acid stronger?
More stable the conjugate base formed the stronger the acid
What is the relative acidity?
Carboxylic acid > phenol > water > alcohol
Reason for RCOOH?
carboxylate ions resonance stabilised 2 oxygen atoms electronegative and EW causes negative charge on RCOO- to be dispersed onto both atoms and EDG decreases acidity by intensifying negative charge on oxygen destabilising carboxylate ion
Reason for phenol?
p-orbital of oxygen overlaps with the pie electron cloud of the benzene ring negative charge on oxygen is delocalised into the benzene ring stabilising phenoxide anion EDG reduce delocalisation of negative charge on oxygen destabilising the phenoxide ion reducing acidity
Reason for ROH?
Alkyl grps are EDG negative charge on oxygen in the RO- is intensified compared to the OH- thus RO- is destabilised and ROH are weaker acids than water EDG reduce acidity
What is a base? What makes it stronger?
Lone pair donor -> more available the lone pair of electrons for donation stronger base
What is the relative basicity?
Aliphatic amines > ammonia > phenylamines > amides (neutral)
Reason for aliphatic amines?
Alkyl grps are EDG enhances availability of lone pair to accept protons -> secondary amines are more basic than primary amines due to ED alkyl grps -> tertiary amines less basic 3 bulky R groups cause lone pair of electrons on N less available due to steric hindrance
Reason for phenylamines?
p-orbital of N overlaps with pie electron cloud of benzene ring lone pair on N delocalised into benzene ring decrease availability of lone pair of electrons on N for donation -> EWG grps enhance delocalisation of lone pair of electrons on N into benzene ring decrease availability of lone pair of electrons for donation
Reason for amides?
Due to delocalisation, lone pair of electron on N less available for donation hence neutral
What is the relative ease of hydrolysis?
Acid chlorides > chloroalkanes > aryl chlorides
Reason for acid chlorides?
Readily hydrolised due to EW oxygen and chlorine atoms intensifying partial positive charge on carbon atom -> strong hcl produced -> gives ppt. of AgCl with silver nitrate (aq) solution -> RCOCL + H2O –> RCOOH + HCL
Reason for chloroalkanes?
Bond strength of C-X -> bond length increase less effective orbital overlap C-X bond easily breaks
Reason for aryl chlorides?
Does not undergo hydrolysis C-Cl strengthened by overlapping p-orbital of Cl and pie electron cloud of benzene ring giving C-Cl partial double bond character + benzene carbon sp2 hybridised C-Cl bond is shorter and stronger than C-X + electron rich benzene ring repels approaching nucleophile
