16 Aromatic Chemistry, amines, polymers, DNA Flashcards
Structure of Benzene?
C6H6
Planar
Intermediate bond length
Equal bond lengths
Very stable
1 delocalised electron per p orbital to form pi cloud.
High melting point
Low boiling point as non-polar so can t dissolve.
Use of aromatic amines
Dyes
Kekule structure and comparison of enthalpies of hydrogenation.
Kekule: clycohexa-1,3,5-triene
Enthalpy of hydrogenation of clycoehexene = -120
Enthalpy for triene = -360 (x3 of -120)
Enthalpy for benzene= -208
So more stable and is formed favourably.
How to prepare primary amines and quaternary amines only?
Primary, use excess ammonia
Quaternary, use excess haloalkane.
Use of quaternary ammonium salts.
Cationic surfactants: +ve and -ve ends
Prevent static
Good conditioner
Useful in industry.
What is the positive/negative inductive effect?
Pushes electron density towards atom, increasing availability to donate electrons.
Draws electron density away from atom, decreasing availability to donate electrons.
Basicity of amines?
Phenylamine–>ammonia–>tertiary amine
How to chemically hydrolyse proteins, difficulty explains why enzymes are used?
6 moldm HCl boiling for 24 hours.
How are disulfide bridges formed.
Between two SH
Hydrogen is removed.
Property of enzymes?
Stereospecific, only break down a single enantiomer.
What does a zwitterion look like?
AA with
extra Proton on amine
deprotonated carboxyl.
(isoelectric)
What form are Amino acids generally in within nature?
Often has a chiral centre, exist naturally as single negative enantiomer to fit into certain cells in organisms.
What do AA look like in acids?
AA with
Protonated amine
From zwitterion + H+
What do AA look like in bases?
AA with
Deprotonated carboxyl
(+H2O)
From zwitter + OH-
