Corpus

Here is the frequency of trades and purchases pronunciation

The Uses of The Word In	Purchase	Trade
All	14516	57236
Spoken	1307	9587
Fiction	1058	3074
Magazine	4516	10524
Newspaper	4320	14859
Academic	3315	19192

Purchase can be followed by
Kinds of word	Example
Noun	For example, the state would expropriate or purchase land, reallocate resources to and often protect-from imports
Verb	We have purchase records going back decades with millions of records in there.
Adjective	…million in deposits, has acquired two banks and has another purchase pending, all of which are worth $617.6 million.
Adverb	Average U.S. families purchase 255 pounds of meat, fish, and poultry each year.
Conjunction	Congrats on your scooter purchase and completion of the motorcycle safety class.
Pronoun	Every Amazon purchase you make teaches that algorithm a little more about you.

Trade can be followed by
Kinds of word	Example
Noun	Pepsico announced a $3 billion trade  agreement with  the Soviet Union.
Verb	The trade fed the increasing girth of its merchants.
Adjective	And those that are peculiar to trade alone and thus hold even for a given level of GDP .
Adverb	If Lopez needs surgery, the Braves will have to trade for a catcher.
Conjunction	Whereby the individual combines agriculture and trade and explores alternative markets.
Pronoun	I'll trade you.

source : http://corpus.byu.edu/coca/