In GC analysis of a mixture of benzaldehyde, benzene, and cyclopentyl bromide, which one will have the shortest retention time and which one will have the longest retention time?
Solution
Retention time : The time taken for solute to pass across chromatography colomn is called as retention time.
Retention time is depends on boiling point of compound. Compounds with low boiling point spent more time in gases and therefore lower boiler compound has short retention time. Compound with high boiling point has large RT.
Now, boiling point of benzaldehyde = 178 o c
cyclopentyl bromide = 138 o c
Benzene = 80 o c
Benzene has lower bp therefore it has shrtesr rt. Then cyclopentyl bromide and langest rt is for benzaldehyde.
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GC Analysis: Predicting Shortest and Longest Retention Times
1. In GC analysis of a mixture of benzaldehyde, benzene, and cyclopentyl bromide, which one will
have the shortest retention time and which one will have the longest retention time?
Solution
Retention time : The time taken for solute to pass across chromatography colomn is called as
retention time.
Retention time is depends on boiling point of compound. Compounds with low boiling point
spent more time in gases and therefore lower boiler compound has short retention time.
Compound with high boiling point has large RT.
Now, boiling point of benzaldehyde = 178 o
c
cyclopentyl bromide = 138 o
c
Benzene = 80 o
c
Benzene has lower bp therefore it has shrtesr rt. Then cyclopentyl bromide and langest rt is for
benzaldehyde.
