Imidazoleglycerol-phosphate dehydratase is an enzyme in the histine biosynthesis pathway. It catalyzes the E1 dehydration of D-erthyro-imidazole-glycerol phosphate to imidazole acetol-phosphate. This is a rare example of a biological E1 reaction, as most biological elimination reactions occur through E1cB instead. In this reaction, D-erthyro-imidazole-glycerol phosphate is first protonated to form a good leaving group. Then, the leaving group is ejected to form the resonance-stabilized carbocation below. Draw curved arrows forming the most stable resonance structure to explain why this reaction goes through an E1 mechanism.

Female luna moths (actias luna) attract males by emitting chemical signals that spread through the air. a male hundreds of meters away can detect these molecules and fly toward their source. the sensory organs responsible for this behavior are the comblike antennae visible in the photograph shown here. each filament of an antenna is equipped with thousands of receptor cells that detect the sex attractant. based on what you learned in this chapter, propose a hypothesis to account for the ability of the male moth to detect a specific molecule in the presence of many other molecules in the air. what predictions does your hypothesis make? design an experiment to test one of these predictions.