- WELCOME TO A VIDEO TUTORIAL THAT WILL INTRODUCE
THE ACID-BASE CHEMISTRY OF AMINES,
AND ESPECIALLY HOW IT'S RELATED TO WATER SOLUBILITY.
LET'S GET STARTED. ALL RIGHTY.
NOW, AMINES ARE PROTON ACCEPTORS.
AND SO, THAT'S A BASE.
AND PARTICULARLY, THEY'RE WEAK BASES.
SO WE'LL DRAW A GENERIC STRUCTURE FOR AN AMINE
AND WE'LL JUST DO A PRIMARY AMINE TO KEEP THINGS SIMPLE.
AND THEN WE WILL REACT THAT WITH AN ACID,
SUCH AS HYDROCHLORIC ACID.
AND BECAUSE HYDROCHLORIC ACID IS A STRONG ACID,
WE WILL SHOW A COMPLETE REACTION ARROW.
SO, IF WE THINK ABOUT OUR UNDERSTANDING
OF ELECTRONEGATIVITY AND POLARITY,
WE KNOW THAT THERE'S A PARTIAL POSITIVE
AND A PARTIAL NEGATIVE HERE,
AND WE HAVE SOME LONE PAIR ELECTRONS.
SO, ELECTROSTATICALLY,
EVEN THOUGH THIS IS NEUTRAL, THE NEGATIVE CHARGE
OF THOSE ELECTRONS IS ATTRACTED TO THE POSITIVE CHARGE
OF THE HYDROGEN ION.
AND HYDROGEN CAN ONLY FORM ONE BOND.
AND CHLORINE IS ELECTRONEGATIVE.
SO, WE GET THIS REACTION OCCURRING. OKAY.
SO YOU'RE NOT RESPONSIBLE FOR THIS REACTION,
BUT I THINK IT HELPS WITH THE--
UNDERSTANDING WHY THINGS ARE GOING ON.
SO, NOW, WE'LL DRAW THE--
SO, NOW, I'LL DRAW THE PRODUCT.
AND SO, I'M GOING TO LEAVE THIS PART THE SAME, ALL RIGHT?
AND THEN THIS LONE PAIR IS WHAT CREATES THE BOND
TO THE HYDROGEN ATOM.
NOW OUR NITROGEN IS NO LONGER IN ITS NEUTRAL BONDING PATTERN.
SO IT WILL HAVE A POSITIVE CHARGE.
AND THE TWO ELECTRONS HERE ARE NOW ALONE
OR COMPLETELY WITH THE CHLORIDE.
THERE'S ANOTHER WAY TO DRAW THIS.
SO I DID THIS TO HELP YOU SEE WHAT'S GOING ON IN THE REACTION.
AND WE COULD SIMPLIFY THIS AND PUT ALL OF THE HYDROGENS
TOGETHER WITH THE POSITIVE CHARGE.
AND THEN THERE'S THE CHLORIDE.
SO, THIS IS VERY IMPORTANT HERE.
WE DESCRIBE THIS AS AN AMMONIUM SALT.
RIGHT? SO IT'S A MORE COMPLICATED IONIC COMPOUND
BECAUSE WE CAN HAVE A LARGE COMPLEX R GROUP.
BUT IT'S STILL FUNDAMENTALLY A CATION AND AN ANION.
AND SO, THESE SALTS OF AMINES, THESE ARE VERY IMPORTANT
BECAUSE THE R GROUPS CAN BE VERY LARGE, RIGHT?
SO IF WE HAVE A LARGE R GROUP, RIGHT?
THEN THE AMINE WILL BE WATER-INSOLUBLE.
RIGHT? AND THAT--
RIGHT? NO--
RIGHT? NO.
WATER SOLUBILITY ARE VERY LOW.
SO JUST LIKE WE SAW IN THE CARBOXYLIC ACID TUTORIAL,
IF YOU HAVE--
IF YOU'VE WATCHED THAT ONE ALREADY,
THE SALTS OF AMINE ARE WATER-SOLUBLE.
RIGHT? IT'S THE POWER OF CHARGE,
HAVING THAT FULL POSITIVE CHARGE
CAN OVERCOME THE HYDROPHOBIC QUALITIES OF THE LARGE R GROUP.
SO THE SALTS OF AMINE ARE WATER-SOLUBLE;
THE POWER OF CHARGE. OKAY.
SO, FOR AMINES IN PARTICULAR,
THIS IS A VERY IMPORTANT THING, RIGHT?
SO WE CAN GO FROM AN INSOLUBLE--
A WATER-INSOLUBLE AMINE TO A WATER-SOLUBLE AMMONIUM SALT.
AND MANY DRUGS ARE-- AND--
ARE AMINES, AND THERE'S A TON
OF BIOLOGICALLY-ACTIVE COMPOUNDS THAT ARE AMINES.
BUT THEY TEND TO HAVE LARGE R GROUPS, AND SO,
THEY'RE WATER-INSOLUBLE. OKAY.
SO, WE WANT TO MAKE THESE AMINES INTO THE AMMONIUM SALTS.
THERE'S SEVERAL REASONS FOR THIS,
THE FIRST ONE I'VE ALREADY MENTIONED,
WE WANT TO CREATE SOMETHING THAT'S WATER-SOLUBLE
SO WE CAN PUT IT IN A SYRUP TO DRINK,
OR INJECT IT, OR PUT IT IN A IV.
ANOTHER THING IS THAT AMINES ARE VERY UNSTABLE
AND THEY'RE PRONE TO DECOMPOSITION.
SO THE AMMONIUM SALTS ARE MUCH MORE SABLE-- STABLE.
AND LAST BUT NOT LEAST, AMINES TEND TO BE VERY STINKY,
AND HAVE LIKE A ROTTEN FISH ODOR.
AND SO, WHEN WE MAKE THEM INTO THE SALT,
THE ODOR GOES AWAY.
SO LET'S LOOK AT AN EXAMPLE
OF HOW WE COULD USE THE ACID-BASE CHEMISTRY.
SO HERE IS A MOLECULE OF EPHEDRINE.
AND THEN WE'RE GOING TO REACT IT WITH HYDROCHLORIC ACID.
AND SO, HERE'S THE AMMONIUM SALT.
AND SO, WE-- THE NAME FOR THE AMMONIUM SALT
WOULD BE EPHEDRINE HYDROCHLORIDE.
SO, WE'LL LEARN, AS WE GO ON, THAT A VARIETY OF ACIDS
COULD BE USED TO CREATE THE AMMONIUM SALT.
AND SO, WE'LL LET EVERYBODY KNOW WHICH ACID WE USED.
NOW, MY SOFTWARE HERE IS A LITTLE FUNKY,
SO THIS BOND GOT ERASED.
BUT NITROGEN HAS THE FOUR BONDS,
AND THAT'S WHY IT HAS THE POSITIVE CHARGE,
AND THIS IS OUR AMMONIUM SALT.
SO WHY IS THIS CHEMISTRY SO IMPORTANT?
WELL, LET'S LOOK AT THE--
AT THE CRITERIA.
WHEN WE HAVE EPHEDRINE,
AND WE WOULD DESCRIBE THIS AS THE--
WE CALL THIS THE FREE BASE. RIGHT?
SO THE FREE BASE OF EPHEDRINE VERSUS THE AMMONIUM SALT. OKAY.
SO, THE FREE BASE HAS A MELTING POINT
OF ONLY 79 DEGREES C. SO IT'S VERY FRAGILE
BECAUSE THIS IS A COVALENT,
A MOLECULAR COMPOUND.
EVEN THOUGH WE HAVE A LOT OF ORGANIC CHARACTER HERE,
IT'S A-- STILL A SALT, AN IONIC COMPOUND.
AND WE KNOW THAT IONIC COMPOUNDS HAVE MUCH HIGHER MELTING POINTS.
SO THIS HELPS TO CREATE MORE STABILITY
AND LESS DECOMPOSITION.
THE FREE BASE OF EPHEDRINE IS VERY FOUL-SMELLING.
THE COMMON NAME OF AMINES ARE, LIKE, PUTRESCENCE,
AND CADAVERINE.
IF YOU'VE EVER SMELL--
SMELLED ROTTING MEAT, YOU WERE SMELLING AMINES.
THE AMMONIUM SALT HAS NO ODOR. OKAY.
SO, IN ADDITION TO HAVING A VERY LOW MELTING POINT,
IT'S ALSO CHEMICALLY-UNSTABLE VERSUS THE AMMONIUM SALT,
WHICH IS VERY STABLE.
AND MOST IMPORTANTLY,
THAT EPHEDRINE HAS VERY LOW WATER SOLUBILITY, RIGHT?
RIGHT BELOW THERAPEUTIC HELP OR BELOW BIOLOGICAL ACTIVITY.
WHEREAS, THE AMMONIUM SALT IS COMPLETELY SOLUBLE IN WATER.
SO THAT'S WHAT HELPS US TO BE ABLE TO USE THESE AMINES,
WHICH ARE VERY BIOLOGICALLY-ACTIVE,
IN MEDICINES.
SO NOW, LET'S PRACTICE A BIT
MORE ON THIS IMPORTANT ACID-BASE CHEMISTRY.
SO WE'LL GO TO THE NEXT PAGE.
ALL RIGHT.
SO, IN THIS FIRST EXAMPLE,
WE WILL JUST SHOW AMINES WITH WATER.
SO HERE WE HAVE A WEAK BASE AND A WEAK ACID.
SO WE'LL USE OUR EQUILIBRIUM ARROW.
AND REMEMBER THE BONDING PATTERN
OF NITROGEN WANTING THREE BONDS AND A LONE PAIR,
AND I'LL GO AHEAD AND DRAW THE WATER MOLECULE OUT,
SO, REMEMBERING IT--
THAT IT'S THIS LONE PAIR ON THE NITROGEN
THAT CREATES ITS BASIC CHEMISTRY.
AND SO, WE WOULD END UP WITH OUR METHYL GROUP, NH3+.
AND THEN HERE, WE WOULD HAVE HYDROXIDE AS THE COUNTERION.
AND THIS CAN HELP US SEE WHY AMINES ARE WEAK BASES,
BECAUSE WHEN WE THINK ABOUT BASES,
WE THINK ABOUT HYDROXIDE.
THIS NEXT EXAMPLE, THIS IS NICOTINE.
AND SO, THERE'S OUR NITROGEN.
WE WILL ADD THE LONE PAIRS.
AND I THINK IT'S HELPFUL TO SHOW THE BOND HERE AND RECOGNIZING,
RIGHT, THAT WE HAVE, ONCE AGAIN,
WE HAVE A POLAR COMPOUND.
AND SO, THOSE LONE PAIRS
ON THE NITROGEN ARE ATTRACTED TO THE PARTIAL POSITIVE CHARGE.
I DIDN'T SHOW IT ON THE WATER UP HERE,
BUT WE'LL JUST FILL THAT IN TO BE COMPLETE.
ALL RIGHTY. SO, VERY--
NOTICE THE SIMILAR PATTERN OF REACTIVITY.
IN THE R GROUPS, YOU CAN SEE WHY, "OH,
IT'S REALLY NICE WHEN WE CAN JUST PUT AN R THERE
AND NOT HAVE TO DRAW THESE CARBONS."
BUT IN THIS CASE, WE'LL SHOW IT.
AND SO, THERE WE HAVE, WE HAVE THE AMMONIUM SALTS.
SO HERE, WE DEFINITELY HAVE OUR AMMONIUM SALT.
SO, THIS IS NICOTINE,
AND THIS WOULD BE DESCRIBED AS NICOTINE HYDROCHLORIDE.
ALL RIGHT.
ONE LAST EXAMPLE TO GIVE YOU CONFIDENCE
WHEN DOING YOUR HOMEWORK.
WE'LL GO AHEAD AND DRAW OUT H-CL AGAIN,
AND RECOGNIZING ITS POLARITY.
AND THERE'S THE LONE PAIRS.
NOW, REMEMBER THAT RIGHT?
SO, ALCOHOLS ARE NOT ACIDS OR BASES.
SO, DON'T LET THAT CONFUSE US, WE'RE FOCUSING ON AMINES,
THAT LONE PAIR ON THE NITROGEN, RIGHT?
IT COMES AND REACTS,
AND FORMS A BOND WITH HYDROGEN. RIGHT?
IF YOU'RE WONDERING THOUGH?
MAYBE YOU'RE WONDERING, LIKE, "BUT THERE'S LONE PAIRS
ON THE OXYGEN,
WHY DON'T THEY REACT?"
LET'S REMEMBER OUR ELECTRONEGATIVITY.
WHO'S MORE ELECTRONEGATIVE, RIGHT?
OXYGEN IS MORE ELECTRONEGATIVE THAN NITROGEN, RIGHT?
ELECTRONEGATIVITY IS ELECTRON GREED.
SO OXYGEN IS TOO GREEDY. RIGHT?
TOO ELECTRONEGATIVE, RIGHT?
SO THE LONE PAIRS ON THE OXYGEN,
OXYGEN'S NOT WILLING TO SHARE.
BUT BECAUSE NITROGEN IS LESS ELECTRONEGATIVE,
THESE LONE PAIRS HAVE THE FREEDOM
TO GO OUT AND PARTICIPATE IN AN ACID-BASE REACTION.
SO NOW, WE'LL DRAW OUR AMMONIUM SALT
LIKE WE HAVE FOR THE OTHER EXAMPLES.
AND SO, THERE WAS THE ORIGINAL HYDROGEN.
AND NOW, WE WOULD HAVE THE HYDROGEN THAT'S CONNECTED
THROUGH THE REACTION WITH THE LONE PAIR.
AND THERE WE GO.
SO, ONCE AGAIN, WE WOULD HAVE OUR AMINE.
IN THIS CASE, WHAT'S THIS?
WHAT KIND OF AN AMINE IS THIS?
PRIMARY, SECONDARY, OR TERTIARY, RIGHT?
THIS WILL BE A SECONDARY AMMINE
AND THIS WOULD BE OUR AMMONIUM SALT.
AND THEN, RECOGNIZING THAT OVER HERE,
THESE WOULD BE WATER-INSOLUBLE.
BUT ONCE WE'VE MADE THE HYDROCHLORIC--
HYDROCHLORIDE SALT, THEY'RE NOW WATER-SOLUBLE.
ALL RIGHTY.
SO, THAT CONCLUDES OUR TUTORIAL
ON AMINES AND THEIR ACID-BASE CHEMISTRY,
ESPECIALLY HOW IT'S RELATED TO WATER SOLUBILITY.
PLEASE TAKE SOME TIME TO WORK A FEW PRACTICE PROBLEMS
TO REINFORCE YOUR UNDERSTANDING OF THIS IMPORTANT CHEMISTRY.