Group Meeting Tumbleweed

I'm sitting at a large table in a small room. The Boss waves a hand in my direction and I rise, taking a green whiteboard marker from the previous victim. 
I'm not terribly nervous. I've been off sick for a few days, and I've been doing repeat reactions, nothing new, nothing unfamiliar. 

And anyway, I'm a third year PhD, I know this stuff like the back of my hand. 

I write out the first reaction. Acid, alcohol, DCC, DMAP. 

"Sorry, what's DCC?" Pipes up an undergraduate. 

I open my mouth to answer. 

"It's a coupling reagent. Dicyclohexyl..." I trail off as the entire contents of my brain vanishes in a puff of smoke. 

Dicyclohexyl what? This is ridiculous, I've written the mechanism out at least 5 times. Why can't I remember the name of the reagent?!

A French masters student saves me and I feel the hot burn of humiliation.                                                                                                     

Moving swiftly on I try to recover and draw out the second route. Except I can't remember it. Not the starting materials or the reagents, even the product. This is silly, I've done this chemistry a hundred times! My pen hovers an inch from the board. I can't turn round, just imaging their faces is bad enough. No one speaks. 

I grope around in my head and it has never seemed so empty. I cant think, nothing is firing! Panic sets in but I manage apply some logic. 

Diazo compounds, therefore usually something to do with tosyl hydrazine. Ditosylhydrazine!! The rest follows and I breathe a sigh of relief. 

As I sit down a headache kicks in. 

That has never happened to me before. It was pretty scary. It was like forgetting to eat lunch or stop at a red light. Stress? Tiredness? No idea. I really hope it never happens again. Especially not in my viva.