10/10/24 Flashcards
what are the resonance forms of benzene? real or imaginary
they are imaginary, the hybrid is real
why do we use resonance forms for benzene
it shows where the carbons and hydrogens are so its helpful for mechanism
what were the two historical classifications of organic molecules
aliphatic and aromatic
what was the original classification of aliphatic compounds
“fat-like” because they didn’t dissolve in water, long chains, no aromatic
what were aromatics originally defined by?
they smell
how do you name a monosubstituted aromatic
name benzene as the parent chain and the substituent as normal
how do you name a disubstituted aromatic ring
assign the appropriate parent name and the correct numbering or position name
what are the various positions in an IUPAC named aromatic ring
ortho is 1,2 disubstituted
meta is 1,3 disubstituted
para is 1,4 disubstituted
how should you name a multi-substituted (3+) aromatic
start the numbering on the parent substituent and only use a numbering system on the substituents
what is a primary difference in reactivity between aromatics and aliphatics
aromatics cannot undergo addition and only undergo substitution
what is needed to make an aromatic undergo electrophillic substitution
a catalyst that acts as a lewis acid to make a very hot electrophile
why are aromatics thermodynamically stable
they are resonance stabilized and gain an energy of 152 kJ/mol
what provides evidence for the hybrid version of benzene
X-ray crystallography shows an average between the bond lengths of single and double bonds, indicating that it is something in between
what are the requirements for aromaticity
the structure must be cyclic, planar, and have a Huckles 4n+2 # of electrons
why must an aromatic system be planar and cyclic
it provides an uninterrupted p-orbital array
