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  • We are gonna have a look at -- today, something that's been hitting the headlines.

  • And we're gonna be talking about this compound here, which it rejoices under the acronym:

  • 2,4-DNP. So that translates to 2,4-Dinitrophenylhydrazyne.

  • You've particularly sort of appreciate it because its trivial name is Brady's Reagent

  • but it also rejoices under the trivial name of Bosche's Reagent.

  • Well, I guess, what we'd like to start the story with is taking you way back

  • to the dawn of organic chemistry, in maybe the 1750's through about 1980's.

  • All of the modern techniques that --as a student or as a member of the public that we learn about,

  • before the martyr of modern analytical techniques, are not available.

  • In fact, the only technique that's available is to measure the melting point of your compound,

  • and that kinda could create some difficulties for you.

  • I've got an example here that we can look at this morning.

  • So this is a popular compound. This is a compound of benzene, it's a derivative

  • and it has an aldehyde group on it.

  • But, as you can see, there's gonna be an intrinsic problem with

  • measuring the melting point of Benzaldehyde. It's a liquid.

  • And if melting points are the only thing you can do, you need a way to be sure that everything that is in

  • that aldehyde or carbonyl class (....)

  • solid that you can then even measure the

  • melting point even in 1750 and black the

  • essence of the ladies reagent or DMP

  • something that you can be sure that the

  • correct an aldehyde or ketone with to

  • give you a solid crystalline reagent and

  • back in the day it would come as a solid

  • so what we're going to do now is we're

  • going to look at the original

  • formulation of the BMP Brady's reagent

  • as it was supplied up until I guess

  • probably about a year and a half ago so

  • we're in here so we're going to do a bit

  • of mining because this has been packaged

  • up this is just secondary containment is

  • the plastic outer shell

  • and now we can get through the least in

  • its original form and you can see is the

  • Dean for the dye that the end for the

  • Nitro and there's the piece of the

  • senile hydrazine Pete and Pete gives you

  • the ladies reagent if the compound is

  • formulated correctly it will be

  • completely spaced and very bored we have

  • no need to worry but if it's dry then

  • that's when all the fun and games and

  • excitement starts but I've deliberately

  • selected / compound where I believe it

  • is dry so I'm just going to point that

  • away from me a little bit and just open

  • up gently so the compounds not terribly

  • volatile so I'm handling listen I could

  • but what we're going to do is probably

  • get a sheet of paper in here so that we

  • can put a little bit out so that you can

  • feel and what you should see if you can

  • spoon some out is a highly bright orange

  • now these are not Cristal's these are

  • aggregates where the small little

  • microcrystals of all started to come

  • together as its drying out when it dries

  • out then the region can become more

  • unstable it can suffer an autocatalytic

  • decomposition the order catalysis is

  • where the product of a reaction

  • encourage the reaction to become faster

  • which generally more products so that

  • becomes even faster and of course that's

  • how you get a runaway reaction and

  • that's what we call an explosion and

  • we're going to test out a little bit

  • later but let's actually focus on why

  • the reagents used and why it's useful

  • and let's take you back again to the

  • 1750 and if you remember we had this

  • compound benzaldehyde we're clearly we

  • don't have a solid so we would like to

  • make a solid derivative not we would

  • have to take this solid and we would

  • have to dissolve it and that'll take us

  • a little bit of time so what we're going

  • to do is use the luxury of modern

  • chemistry and what I've done here is

  • actually so influenced me to his one eye

  • pattern

  • so this is just a solution of this

  • orange compound i put it into solution

  • and so what you should see here i hope

  • is that bright or institution come up

  • right okay so we're going to try and

  • turn I've been out of hiding to a into a

  • solid now i just mentioned that canvas

  • like to do all of their reactions in

  • solution so we're going to use methanol

  • we're just going to use that as a

  • solvent for the reaction so we need to

  • get both are orange hydrazine and our

  • carbonyl compound in the same solution

  • so I'm going to take some benadryl

  • divide here and what I'm going to do is

  • to a not terribly stoichiometric

  • reaction clue we're going to take

  • that'll probably about the about 250 200

  • 300 million dancing like that will put

  • that into the solar put the lid back on

  • here and now the high desert very nice

  • smell of almonds but it's like toxic

  • toxic and now we need to switch and see

  • if we can get this to maker of

  • precipitate so let's see

  • benzaldehyde got a mass of about a

  • hundred we're about two million miles in

  • here this is about point two molar so we

  • need a illegal about this with the rate

  • of reaction of DMP o Brady's raging with

  • aldehydes depends on the substrate and

  • it can take anything from instantaneous

  • up to several hours

  • alright so let's just stop there

  • oh look there you go

  • so as you can see we've got almost

  • instantaneous reaction we've produced

  • from our original liquid benzaldehyde a

  • large clump of a bright orange-yellow

  • derivative chemist like to use names to

  • describe the derivative we started with

  • the hydras leave for this derivative of

  • the hydro-zone ok so we've talked a lot

  • about the chemistry of the MP and white

  • really useful but it won't have escaped

  • your attention that in media recently

  • there's been a lot of concern over

  • Brady's reagent pnp as a potential

  • source of the explosion the compound as

  • it was originally formulated damn

  • perfectly safe in the modern version

  • that we've shown you perfectly safe

  • the compound does have a reputation mode

  • for being what is called shock-sensitive

  • meaning that is the compound is

  • subjected to friction or sudden energy

  • through an impact it can detonate that's

  • not so well described actually in the

  • scientific literature and so in the

  • cause of science

  • what we're going to do is try and make a

  • brief investigation of a small and

  • therefore potentially safe scale to

  • indicate what the degree of shock

  • sensitivity is as formulated in wet that

  • shouldn't really be that much shock

  • sensitivity and ladies region but like

  • there's very little data and we're not

  • going to take any chances for I I'm not

  • gonna put on not just a face mask but

  • this is an explosion facemask and it

  • exposed it will protect my face still

  • and I'm gonna gonna lose any fingers so

  • i'm going to go for some protective

  • gloves as well to chest the toxin today

  • we are going to use this highly

  • expensive scientific piece of apparatus

  • available from any good hardware store

  • and we're going to strike the compound

  • not excessively hard because it should

  • lead that if it's going to go so I'm

  • going to give it a light tap and then

  • we'll see 123 that I think it's me

  • missing so we'll do that again

  • 12

  • three we struck the compound you might

  • want to come in and have a look at back

  • and free here at the black this is where

  • it was struck with a hammer quite

  • vigorously no effect whatsoever you can

  • make the comparison against the material

  • that jumped off the front

  • these are exactly the same color and

  • that's quite a decent strike

  • okay from what we should do now is let's

  • try the compound out and see if it makes

  • a difference

  • so again the literature is not too clear

  • and in view of safety concerns

  • we're going to be a little bit vague

  • about how long we're going to drive is

  • compatible we're going to put it on this

  • hot plate that you can see in the back

  • of the hood you can see the red flashing

  • light indicating that the hot plate is

  • heating and if you look closely at the

  • dials here you can see it said it just

  • over 100 degree C so that should drive

  • offering water and then we'll run our

  • shop test we're gonna put that on the

  • hot plate and now it's my turn the fire

  • code retire to a safe distance

  • ok so we're backing part two of the

  • great shock destination story so while

  • we've been away having a cup of tea

  • what we have left is our hot plate which

  • you can see in the background there and

  • we've been cooking up rtmp so we're at

  • the top here and on 321 this compound is

  • not excessively shock-sensitive ok but

  • what i should add at this point of

  • courses we've done this under very

  • controlled condition was done this with

  • a very small amount of material the

  • compound has a reputation for shock

  • sensitivity therefore there have been

  • detonations in the park

  • clearly we've done this for you today so

  • that you can see and feel confident in

  • that in the chemistry but that i would

  • advise you to take in 14 pound sledge

  • hammers and Dustin's full of this stuff

  • expand very rapidly one of the things

  • that Idol was interesting is that when

  • the bubble catches fire burning gas

  • continues to move up

We are gonna have a look at -- today, something that's been hitting the headlines.

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布拉迪試劑 - 視頻週期表 (Brady's Reagent - Periodic Table of Videos)

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    林宜悉 發佈於 2021 年 01 月 14 日
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