text: Yo, check it out, I got a story to tell,
  'Bout a photocycloaddition reaction, it's hella swell.
  A 4',5'-dihydropsoralen derivative, you know what I mean,
  Mixed with thymine in a solution, it's a sight to be seen.
  
  Using a bichromophoric model, number 8 in the game,
  Two rings connected by a tetramethylene chain.
  In water, this molecule, it's got some interactions,
  Ring-ring stacking, UV and NMR confirmations.
  
  Irradiation at 365 nm, concentration on the high,
  Dimerization reaction, regio- and stereo-selective, oh my!
  Them 3,4 double bonds, they get involved,
  Psoralen moities, yo, they be evolved.
  
  But hold up, extreme dilutions, we gotta take it slow,
  Less than or equal to 2.10(-5) M, watch it go.
  Intramolecular reaction, it's exclusive, no doubt,
  Formation of a 3,4 cis-anti adduct, that's what it's about.
  
  But wait, when we hit it with 254 nm light,
  The whole reaction, it takes a flight.
  Reversed completely, like a rewind in time,
  These results got me thinking, yo, they blow my mind.
  
  Let's talk about them homologous models, fam,
  Without the hydrogenated furan ring, damn.
  Same deal, 3,4 cis-anti adducts all the way,
  No other products, they don't come into play.
  
  Seems like saturating the furan ring is the key,
  Boosting the quantum yield, it's clear to see.
  From 0.01 to 0.18, that's the range,
  And the 4',5'-dihydropsoralen's triplet state, it's engaged.
  
  That's the story, the science, the rap in full flow,
  Photocycloaddition reaction, now you know.
  From UV to NMR, the results they bring,
  In the world of chemistry, it's a beautiful thing.