Chem 4:6 - Aromatic Chemistry Flashcards
What does benzene have on each corner of its shape?
A carbon and a H
What can arenes have that’s different from benzene?
A FG can replace one or more of the H atoms in the structure
Benzene is unsaturated but what does it not do ?
form addition compounds
What is each carbon bond in benzene in terms of single and double bonds?
An intermediate between a single and double bond
Carbon has 3 covelant bonds, what to?
1 to H
2 to 2 other C atoms
what orbital is the 4th electron of the C-C bond in?
The P orbital
there are 6 of these electrons in the p orbital, what characteristics do they have?
they are delocalised
they form a region of density above and below ring
Do they deloc e’s make benzene stable?
yes
What are 3 physical properties of benzene?
-Colourless liq at RT
-Boils at 353K/ Melts at 279K
(MP high because benzene packs together well in solid state therefore harder to separate.
-Separation must occur for melting to happen
What don’t arenes mix well with? and what do they mix with ?
Water not good
Do mix with hydrocarbons and other non polar substances
What is the most common reaction type in aromatic compounds?
Electrophillic substitution
Why are electrophilic subs reactions the most common in aromatic compounds?
Ring has high e density therefore attacked by electrophiles
Ring is stable therefore needs energy to be put in to break ring
What 4 characterstics do they combustion of amines have?
- arenes burn in air with smoky flames
- high C-H ratio
- Unburned C in air ususally produces soot
- Smoky flame will suggest AROMATIC COMPOUND.
Decsribe the reaction between an arene and an electrophile
- High e density attracts the electrophile
- Bond forms between C and El+
- But C uses e from delocalised system to do this
- This destroys aromatic system
- C loses H+ ion
- Electrophile substitutes H
How is NO2+ generated?
H2SO4 + HNO3»_space;»> H2NO3+ + HSO4-
-the H2SO4 is a stronger acid than HNO3 therefore donates proton to HNO3 to make H2NO3
-H2NO3 then loses a water mol leaving NO2+
(nitronium ion)
- Overall equation:
H2NO3+»_space;»> NO2+ + H2O
