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Hetrocycle
Any system containing one or more hetreoatoms
Heteroatom
Atom other than C
Pyridine
Isoelectronic with benzene
Difference between pyridine and benzene
CH group in benzene is replace with N
What is the geometry in pyridine
Trigonal planar
Bond angle - 120
What does each C contribute to the pi cloud in pyridine
1
What does the pi cloud contain
Aromatic sextet of e-
What happens the lone pair of e- with the N in pyridine
Not involved in aromatic sextet
What does the loan pair of e- not being involved in the aromatic sextet mean
basic and a good ligand
What does protonation use in pyridine
Nitrogens lone pair of e-
How is pyrrole able to be aromatic
Because lone pair of e- on N is part of aromatic sextet
Observed geometry in pyrrole
Trigonal planar
Bond angle = 120
How is aromatic stability quantified
Measuring heats of hygrogenation
What does the aromatic sextet of pyrrole contain
4 pi e- and 2 e- from N lone pair
Acidity/ baseness of pyrrole
Very weakly basic
What does imidazole contain
Pyridine like N
Pyrrole like N
Histadine
Naturally occurring a amino acid
What happens pyrrole like N in Histidine
Complexed to metal ions
What happens histidine at physiological pH
Imidazole group and its conj acid are in equilibrium and accounts for the buffering properties
What does imidazole group and its conj acid are in equilibrium enable
His residue in proteins to act as buffer
Does pyridine undergo electrophilic aromatic substitution
Rarely
Has low reactivity
Electron withdrawal by N makes pi system less e- rich and less attractive to electrophiles
Does pyrrole undergo electrophilic aromatic substitution
Yes
Nó catalyst or heat required
What do DNA and RNA consist of
Sugar/ phosphate backbone to which N bases are attached
Difference between DNA and RNA
Type of sugar and which bases are used
Ring bases in DNA / RNA
Pyrimidine
Ring system bases in DNA / RNA
Purine
