Replacement of theΒ meso Β methine carbon atoms of porphyrins with heteroatoms represents a powerful strategy for tuning their optical and electronic properties. In particular, 5βoxaporphyrin is an attractive target due to its importance as an intermediate in heme catabolism. In this work, we describe the synthesis and properties of a freeβbase 5βoxaporphyrinium cation, which was prepared by the ringβclosure of a bilindione with trifluoromethanesulfonic anhydride. This freeβbase 5βoxaporphyrinium cation exhibits dual fluorescence originating from its unique NH tautomerism. In contrast to normal porphyrins, theΒ cis Β form of the 5βoxaporphyrinium cation is more stable than theΒ trans Β form due to the effective delocalization of its positive charge. We thus demonstrate here thatΒ meso βmodified Β heteroporphyrins enable the manipulation of NH tautomerism in porphyrinic macrocycles.
https://ift.tt/34oyswK
Does anyone know how to draw the two tautomers of acetylacetone (diketo and keto-enol) such that steric interactions are minimized? Thanks!
MD calculations have shown that in zeolites, 1,2-, 1,3- and 1,5-hydride shifts between secondary carbocations occur frequently on a scale of picoseconds. (Cnudde et al.)
In regards to the Biginelli Reaction:
- Why do strongly acidic solutions not hinder the reaction of the NH2 group of urea with the aldehyde?
- Why is the enamine-like tautomer more favored over the imine-like tautomer? Is this because urea is less basic than primary N-atoms which typically form imines, and less basic N-atoms (namely secondary) form enamines?
I don't want to step on anybody's toes here, but the amount of non-dad jokes here in this subreddit really annoys me. First of all, dad jokes CAN be NSFW, it clearly says so in the sub rules. Secondly, it doesn't automatically make it a dad joke if it's from a conversation between you and your child. Most importantly, the jokes that your CHILDREN tell YOU are not dad jokes. The point of a dad joke is that it's so cheesy only a dad who's trying to be funny would make such a joke. That's it. They are stupid plays on words, lame puns and so on. There has to be a clever pun or wordplay for it to be considered a dad joke.
Again, to all the fellow dads, I apologise if I'm sounding too harsh. But I just needed to get it off my chest.
Do your worst!
I'm surprised it hasn't decade.
For context I'm a Refuse Driver (Garbage man) & today I was on food waste. After I'd tipped I was checking the wagon for any defects when I spotted a lone pea balanced on the lifts.
I said "hey look, an escaPEA"
No one near me but it didn't half make me laugh for a good hour or so!
Edit: I can't believe how much this has blown up. Thank you everyone I've had a blast reading through the replies π
It really does, I swear!
Because she wanted to see the task manager.
Theyβre on standbi
Pilot on me!!
Nothing, he was gladiator.
Dad jokes are supposed to be jokes you can tell a kid and they will understand it and find it funny.
This sub is mostly just NSFW puns now.
If it needs a NSFW tag it's not a dad joke. There should just be a NSFW puns subreddit for that.
Edit* I'm not replying any longer and turning off notifications but to all those that say "no one cares", there sure are a lot of you arguing about it. Maybe I'm wrong but you people don't need to be rude about it. If you really don't care, don't comment.
BamBOO!
When I got home, they were still there.
What did 0 say to 8 ?
" Nice Belt "
So What did 3 say to 8 ?
" Hey, you two stop making out "
I won't be doing that today!
[Removed]
Where ever you left it π€·ββοΈπ€
This morning, my 4 year old daughter.
Daughter: I'm hungry
Me: nerves building, smile widening
Me: Hi hungry, I'm dad.
She had no idea what was going on but I finally did it.
Thank you all for listening.
There hasn't been a post all year!
You take away their little brooms
It was about a weak back.
