Derivatives of Aromatic Hydrocarbons Flashcards
hydrocarbons containing sigma bonds and delocalized pi electrons between carbon atoms in a ring
aromatic hydrocarbon
aromatic hydrocarbons are known as aromatic due to their __ __
pleasant smell
benzene-CH3
toluene
benzene-OH
phenol
benzene-NH2
aniline
benzene-C(=O)CH3
acetophenone
benzene-CHO
benzaldehyde
benzene-COOH
benzoic acid
benzene-CN
benzonitrile
1,2-dimethylbenzene
ortho-xylene
benzene-CH=CH2
styrene
aromatic compounds are also called as __ or __
- aromatics
- arenes
aromatic compounds are characterized by the presence of __ or __ __ and are __ __ __
- one or more rings
- uniquely stable structures
result of strong bonding arrangements between certain pi electrons of molecules
uniquely stable structures
Two categories of aromatic compounds
- Benzenoids
- Non-benzenoids
contains benzene rings
benzenoids
exhibits an aromatic behavior but does not contain a benzene ring
non-benzenoids
polarity of aromatic compounds
non-polar
solubility of aromatic compounds in water
non-miscible
reactivity of aromatic compounds
usually unreactive
carbon to hydrogen ratio of aromatic compounds is __
high
aromatic compounds flame
sooty yellow flame
classification of aromatic compounds
- nuclear-substituted compounds
- side chain substituted compounds
any aromatic compound whenever any substituent or functional group is directly linked to the benzene ring
nuclear-substituted compounds
any aromatic compounds if the functional group is available in the side chain of the ring
side chain substituted compounds
one of the most commonly known aromatic compounds with chemical formula C6H6
benzene
benzene is a naturally occurring substance produced by __ and __ __
- volcanoes
- forest fires
benzene is said to be highly toxic in nature and is also known as a __
carcinogen
average mass of benzene
78.112 g/mol
property of cyclic and planar molecules having resonance bonds exhibiting more stability than the connective or geometric arrangements within the same kind of atoms
aromaticity
Huckel’s Rule of Aromaticity
- planar
- conjugated
- presence of (4n+2)=π (n=2, 6, 10, 14)
entire molecule must be fully planar
planarity
entire molecule must have complete delocalization of the pi electrons
conjugated
proposed huckel’s rule of aromaticity
Erich Huckel
when one of the positions on the ring has been substituted with another atom or group of atoms
monosubstituted benzene
how are monosubstituted benzenes named
using the substituent followed by benzene without number to indicate position
when two of the positions on the ring has been substituted with another atom or group of atoms
disubstituted benzene
disubstituted benzenes can be named __, __, and __ or numbers
- ortho
- meta
- para
benzene with more than two substituents
polysubstituted derivative
benzene can be found in household products like:
- glue
- adhesives
- cleaning supplies
- paint strippers
- gasoline
- tobacco smoke
used to make latex, synthetic rubber, and polystyrene
styrene
styrene is produced using
ethyl benzene
sources of aromatic hydrocarbons
- high temperature distillation of coal tar
- heating petroleum at high temperature and pressure over a catalyst
organic reactions wherein an electrophile replaces an atom that is attached to an aromatic ring
electrophilic aromatic substitution
is preserved in an electrophilic aromatic substitution reaction
aromaticity of aromatic system
most common electrophilic substitution reactions
- halogenation
- nitration
- sulfonation
- friedel-craft alkylation
halogen group replaces hydrogen
halogenation
NO2 group replaces hydrogen
nitration
SO3H group replaces hydrogen
sulfonation
an alkyl group replace hydrogen
friedel-craft alkylation
resonance-stablized carbocation intermediate
sigma complex
the process (chlorination or bromination) makes use of a __ __
Lewis acid
Lewis acid in chlorination or bromination takes a pair of electrons to form a permanent bond dipole in the __ bond or the __ bond
- Cl-Cl
- Br-Br
as a result of the dipole, the bromine or chlorine has a __ __ __
formal positive charge
the formal positive charge of bromine or chlorine makes the group electrophilic enough to simply overcome the
activation energy produced by benzene ring’s loss of aromaticity
in halogenation of benzene, it requires __ to initiate the reaction
catalyst
due to high stability of benzene, there is low reactivity. Thus, bromine or chlorine is reacted with __ or __ to give an electrophile
- FeBr3
- FeCl3
reaction that replaces the hydrogen with an electrophile
electrophilic aromatic substitution reaction
friedel-crafts alkylation is an electrophilic aromatic substitution reaction in which a __ is attacked by a __ __
- carbocation
- pi bond
sulfonation is a reversible reaction that produces __ __
benzenesulfonic acid
sulfonation is a reversible reaction that produces benzenesulfonic acid by adding __ __ and __ __ __
- sulfuric trioxide
- fuming sulfuric acid
changes to a system equilibrium will result in predictable and opposing changes to achive new equilibrium state
Le Châtelier’s Principle
Le Châtelier’s Principle:
reactant concentration increases
reactant concentration increases
Le Châtelier’s Principle:
pressure increases
side with fewer gas molecules is favored
Le Châtelier’s Principle:
temperature increases
endothermic reaction is favored
Le Châtelier’s Principle:
product concentration increases
reactant formation is favored
Le Châtelier’s Principle:
pressure decreases
side with more gas molecules is favored
Le Châtelier’s Principle:
temperature decreases
exothermic reaction is favored
EAS
electrophilic aromatic substitution
effects of substituents on EAS
- rate of reaction of the ring
- position of attack
position of attack called __ __
directing effects
rate of reaction (2)
- activated rings
- deactivation
substituents on the ring donate electrons and increase EAS reaction rates
activated rings
substituents on the ring withdraw electrons and decrease EAS reaction rates
deactivation
position of attack (2)
- ortho-, para-
- meta-
electron donating groups (D) direct the reaction ot the ortho- or para- position
ortho-, para-
the withdrawing group directs the reaction to the meta position, which means the electrophile substitutes for the hydrogen on carbon 3 relative to the withdrawing group
meta-
useful tool in predictin the behavior of aromatics
theory of reactivity and orientation
when a monosubstituted benzene undergo electrophilic substitution reaction, the group already present in the rings controls the __ _ __ and the __ __ __ __
- rate of reaction (reactivity)
- site of electrophilic attack (orientation)
the attacking electrophile is directed towards the position that provides the __ __ __
most stable intermediate
aromatics exhibit high stability due to the __ _ __ _ __ __
delocalization of electrons in pi system
the reactivity of aromatic ring depends on the __ __ or __ __ attached to it
- electron-donating
- withdrawing groups
electron–donating groups
activators
electron-withdrawing groups
deactivators
increase the electron density on the ring, making it more susceptible to electrophilic attack
electron-donating groups
decrease the electron density on the ring, making it less reactive towards electrophiles
electron-withdrawing groups
in presence of substituent that donates electrons, the attacking electrophile is directed towards the position that has the least destabilizing effect on the intermediate. what are these positions
ortho (1,2), para (1,4) position
all electron-donating are in what position
ortho- and para- position
all deactivators are __ directors, except halogens which are deactivators but are __ directors
- meta-
- ortho- and para- directors
common chemical reaction that involves the introduction of oxygen atom into the side chain of an organic compounds
oxidation of alkyl side chains
most common reagents in the oxidation of alkyl side chains
- potassium permanganate (KMnO4)
- chromium trioxide (CrO3)
- potassium dichromate (K2Cr2O7)
application of aromatics
- perfume and fragrances
- food and beverages
- pharmaceuticals
- cosmetics
- cleaning products