Nucleophiles and Electrophiles: Crash Course Organic Chemistry #12 - Free Educational videos for Students in K-12

Nucleophiles and Electrophiles: Crash Course Organic Chemistry #12 - By CrashCourse

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00:0-1	You can review content from Crash course Organic Chemistry with
00:02	the Crash course app available now for android and IOS
00:05	devices . Hi , I'm dave okay Chakravarty and welcome
00:08	to Crash course Organic Chemistry . The word stem file
00:11	, which is derived from the greek fellows meaning loving
00:14	has been used with other prefixes or suffixes to suggest
00:17	the love of just about everything . There's a philodendron
00:20	, which is a plant that loves to climb trees
00:23	or technophile , which describes a lover of new technologies
00:26	. I might consider myself a bibliophile and I lure
00:29	a file to profess my love of books and cats
00:32	and maybe we can call ourselves organa files as people
00:35	who love organic compounds in this episode though , will
00:38	specifically be looking at two very important files , electro
00:41	files , lovers of electrons and nuclear files . Lovers
00:44	of the molecules positive regions . Over the last few
00:47	episodes , we've been thinking about molecular hotspots , places
00:50	on a molecule where positive charges and negative charges show
00:53	up now it's time to think about what happens at
00:56	these hotspots electro files and nuclear files . So my
00:59	fellow organa files , let's get to it . Yeah
01:10	. Yes . In the last episode we discussed Bronston
01:15	, Lowry acids and bases where the acid is a
01:17	proton donor in the basis of proton except er but
01:20	there are molecules out there called Lewis acids and bases
01:23	which accept or donate electron pairs instead of protons .
01:26	Specifically Lewis acids , except a lone pair of electrons
01:30	and Lewis bases donate a lone pair of electrons .
01:33	LeWIS bases often include atoms with lone pairs like nitrogen
01:36	and oxygen . For example , ammonia and water are
01:39	LewiS bases . Other Lewis bases are negatively charged atoms
01:43	like chloride or groups of atoms like hydroxide . Generally
01:46	lewis bases are recognizable because they have lots of electron
01:49	. So we call them electron rich . Lewis bases
01:52	are also nuclear files . Technically if we go back
01:56	to our word stem file , this means nucleus loving
01:59	. But when it comes to reactions in organic chemistry
02:01	being a nuclear file beans , they love to interact
02:04	with positive charges or positive regions on another molecule .
02:07	Think of it kind of like a superhero with the
02:10	grappling hook . A nuclear file is kind of looking
02:12	for a positive charge . It can throw its electrons
02:15	toured and grab onto on the flip side . Lewis
02:17	acids are positively charged atoms like a proton or molecules
02:21	that are short a pair of electrons from an octet
02:23	and have an empty p orbital . Like boring Bh
02:26	three boring only has six electrons with neutral and it's
02:29	empty P orbital can accept electrons . This general definition
02:33	doesn't include compounds like phosphorus Penta chloride that can be
02:37	considered nontraditional lewis acids , some of which will meet
02:40	later in the series . Lewis acids are electron poor
02:43	, which is why they're willing to accept lone pairs
02:45	. And lewis acids are also electro files going back
02:48	to our word stems , this means electron loving and
02:52	inorganic chemistry reactions . Being an electro file means they
02:55	love negatively charged electrons and other molecules and can even
02:59	provoke them into interacting sometimes to continue my grappling hook
03:02	metaphor , think of an electro file as a molecule
03:05	with a big red video game like target on it
03:08	saying grappling hooks here . One of the most important
03:11	electro files we'll see throughout these videos are carbo cat
03:14	ions . These are molecules with an sp two hybridized
03:17	carbon atom and an empty P orbital which creates a
03:20	positive charge . Keeping formal charges in mind . We
03:23	can see that the carbon only has three bonds which
03:25	contributes three valence electrons . A neutral carbon atom has
03:29	four valence electrons , so four minus three is positive
03:32	one and therefore it has a plus one formal charge
03:36	now that we have nuclear files and electro files as
03:38	our players for today . Let's get into the fun
03:41	stuff . What happens when they run into each other
03:44	in a lab , when a nuclear file reacts with
03:46	anything , we call it a nuclear filic attack .
03:49	If we think of organic reactions as carefully choreographed fight
03:52	scenes , a nuclear filic attack is just one move
03:55	in the superhero skill set , it can be one
03:58	step in a larger chemical reaction or a powerful move
04:01	all on its own . In a nuclear filic attack
04:03	, nuclear files are always the aggressor and do the
04:06	attacking . So curved reaction arrows always start on the
04:10	nuclear file and are drawn to the electro file .
04:12	Electro files aren't just innocent bystanders though , because they
04:15	love electron so much they can sometimes provoke a nuclear
04:19	file into attacking . Kind of like when you want
04:21	someone to do something and you keep asking and asking
04:25	and asking until they give in or you taunt them
04:28	a little bit to go them on . Like I
04:30	mentioned , a nuclear feel like attack can be part
04:32	of a larger multi step chemical reaction . But in
04:34	this episode we're going to start simple with a one
04:37	step reaction involving a nuclear file and an electro file
04:41	. You've got to learn how to punch before you
04:43	start a martial arts film , you know ? So
04:45	here we have two compounds , a hydroxide ion and
04:48	one Clara butane . The hydroxide has lots of electrons
04:51	and that negative charge . So it's pretty easy to
04:54	figure out that it's our nuclear file . It's a
04:56	little trickier to see that one . Clara butane is
04:58	our electro file though . For that we have to
05:01	remember what we learned in a previous episode about polarity
05:04	. This chlorine carbon bond is polarized seriously . I'm
05:07	not joking when I say that we're assembling an organic
05:10	chemistry toolkit . All this knowledge builds in this bond
05:13	. The electro negative chlorine is pulling electrons towards itself
05:17	which gives the carbon a partial positive charge and the
05:19	chlorine a partial negative charge . This makes that carbon
05:23	and electro file , which is pretty attractive to the
05:25	hydroxide ion . So when this reaction takes place ,
05:28	the hydroxide attacks that carbon and donates electrons . This
05:32	is hydroxide is grappling hook move I guess hydroxide is
05:35	basically batman here in the carbon chain is the side
05:38	of a Gotham city building he wants to climb .
05:40	Our carbon is only capable of making four bonds .
05:43	So before we finish the reaction , we have to
05:45	make sure we're not breaking the rules of science .
05:48	The chlorine takes a pair of electrons with it to
05:50	become a chloride ion and butin one all is left
05:53	behind . So fight sequence done now there are different
05:56	kinds of nuclear filic attacks that have different names for
05:59	now we can just call this particular reaction and nuclear
06:02	Felix substitution because the hydroxide basically substitutes in for the
06:06	chlorine . We'll talk more about nuclear Felix substitution is
06:09	and get more specific about naming them in a future
06:12	episode . But it's helpful to start getting familiar with
06:15	the general term for this kind of reaction . Now
06:17	now you don't have to take my word for it
06:20	that this reaction happens and that our fight sequences ended
06:22	successfully with Butin one all we can actually see that
06:26	this reaction happened with an experimental tool we've learned in
06:28	this series infrared spectroscopy or IR IR provides information about
06:33	the functional groups present in molecules by measuring bond vibrations
06:37	and one of the most recognizable functional groups and I
06:40	are is alcohol , which we have here in butte
06:42	one . Also , if the nuclear filic attack goes
06:45	as planned , we should see a big change in
06:47	the spectrum to see this in action . Here's the
06:50	IR spectrum for one Clara butane and here's the spectrum
06:53	we get for the product of this particular reaction .
06:55	There is a strong broad peak at 3300 wave numbers
06:59	which is the O . H bond of an alcohol
07:01	. So we can be pretty sure that button one
07:03	hole was formed . So organic chemistry isn't really just
07:06	magic . And guessing we can confirm what we draw
07:09	on paper for our nuclear filic attack choreography with experimental
07:13	tools like infrared spectroscopy . The reaction we just looked
07:16	at started nuclear file hydroxide . It came in strong
07:19	with a negative charge and attack that partial positive carbon
07:22	in one fell swoop . But like I mentioned earlier
07:24	, there are strong electro files out there too ,
07:26	which pester nuclear files into attacking . And carbo cat
07:30	ions are some of the most pesky characters out there
07:33	, taunting enough that even a weak nuclear file like
07:36	water , will attack them . These nuclear feel like
07:38	attacks are slightly more complicated fight sequences to choreograph .
07:42	So they usually happen in two steps . Let's look
07:45	at this example with a carbo cat , iron as
07:48	our electro file and water as our nuclear file .
07:50	The first step of the nuclear feel like attack is
07:52	still initiated by the nuclear file . Water , a
07:56	lone pair of electrons on oxygen attacks that positively charged
07:59	carbon and donates electrons . Water shoots out a two
08:03	electron grappling hook and makes a bond . Then in
08:05	the second step , a second water molecule gangs up
08:08	on this grappled molecule and gets in on the action
08:11	In this case . Because the second water molecule attacks
08:14	of proton , we can call this a deep pronation
08:16	. It might be tempting to show the electrons going
08:19	straight to the positive charge on the oxygen . But
08:22	be careful oxygen obeys the octet rule and that move
08:25	would give it 10 electrons . Before we can finish
08:27	the reaction , we have to make sure we're not
08:29	breaking the rules of science and hydrogen can't have two
08:32	bonds . So a pair of electrons from the hydrogen
08:35	oxygen bond hops to the positively charged oxygen atom ,
08:39	neutralizing the charge and a hydro nian molecule breaks away
08:42	from the scuffle fight sequence . Done to some of
08:46	this two step reaction , the carbo Catalan undergoes a
08:48	nuclear filic attacked by one molecule of water . Then
08:51	it gets deep originated by a second molecule of water
08:54	. So we're left with an alcohol and a hydro
08:56	nia . My on to show another two step reaction
08:58	and practice or fight choreography with slightly different characters .
09:01	Let's look at a different kind of nuclear file molecules
09:04	with double and triple bonds like Calkins , al kinds
09:07	and carbon Neil groups . Nuclear files are just groups
09:10	with lots of electrons . So all these fit right
09:13	in . For example , let's look at the reaction
09:15	of cis butte tooling and hydrogen bromide . Remember hbr
09:19	is a strong acid and ionized is completely to form
09:22	H plus and br minus . The alcan has a
09:25	double bond . So it's our nuclear file and ready
09:27	to attack our electro file . The proton . So
09:30	the double bond donates electrons by throwing it's pi electrons
09:33	as a grappling hook and hooking the proton . When
09:35	the falcon uses these two electrons to attack the proton
09:39	. One of the two carbons previously involved in the
09:41	double bond is short an electron and ends up positive
09:44	. Now we're left with a super pesky carbo cat
09:46	eye on is an electro file and the negatively charged
09:49	bromide ion as a nuclear file , the positive charge
09:52	on the carbo cat ion is irresistibly taunting to the
09:55	bromide ion . So for the second step of this
09:57	reaction , the bromide does a nuclear filic attack and
10:00	forms to brahma butane fight sequence . Done . These
10:04	two ended up as one unified dynamic duo or molecule
10:08	. We're going to end this episode with one final
10:10	nuclear file that you may have heard of before as
10:13	a potent poison in victorian era mystery novels and beyond
10:17	cyanide . It's a carbon atom triple bonded to a
10:19	nitrogen atom and the carbon carries a negative charge .
10:23	But now's our chance to see cyanide is way more
10:25	than just a poison . It's a pretty cool molecule
10:28	because it can do a nuclear filic attack to form
10:30	a carbon carbon bond and being able to add carbons
10:34	together is important in organic chemistry because it helps us
10:37	make supersized molecules such as big drug molecules and medicine
10:41	as a strong nuclear file . Cyanide can attack carbon
10:44	one in an electro file like one bromo two metal
10:46	heck saying this is another one of those nuclear Felix
10:49	substitution . The cyanide latches on with a bond and
10:53	pushes out the bro meet as a bromide ion .
10:55	We'll see in future episodes how carbon chains with cyanide
10:58	substitutes are super useful as gateways to other functional groups
11:02	or just for elongating a shorter change . So with
11:04	that we've gotten pretty familiar with the fight choreography of
11:07	a nuclear filic attack . The arrows start with the
11:09	electron pairs on our nuclear file and end on the
11:12	positive region of our electro file . And with this
11:15	knowledge we're getting closer to being able to puzzle out
11:17	, not memorize lots of complicated reactions that make organic
11:21	chemistry notoriously tricky . In this episode we have learned
11:24	that nuclear files are louis basis that donate electrons and
11:27	attack electro files . Electro files are lewis acids that
11:31	are attacked by nuclear files . Ir spectra can help
11:35	us understand if a reaction really does happen and cyanide
11:39	is more than just a poison next time we'll get
11:42	further into the nitty gritty of air pushing and reaction
11:44	mechanisms . Let's face it , No one wants to
11:47	memorize thousands of reactions . And if we can learn
11:50	how to write good mechanisms , we won't have to
11:52	. Thanks for watching this episode of Crash Course Organic
11:55	Chemistry . If you want to help keep all Crash
11:57	Course free for everybody forever , you can join our
12:00	community on Patreon . Yeah .

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