- WELCOME TO HYDROCARBONS PART 1B,
THE HOMOLOGOUS SERIES.
THIS VIDEO TUTORIAL WILL INTRODUCE US TO THE IDEA
OF THE HOMOLOGOUS SERIES FOR ORGANIC MOLECULES.
LET'S GET STARTED. ALL RIGHT.
NOW, AS WE BEGIN LEARNING HOW TO NAME ORGANIC COMPOUNDS,
WE NEED TO KNOW THE ROOT OR THE PARENT'S NAME.
AND THIS WILL BE ONE OF THE LONGEST CARBON CHAINS IN THE--
IT WILL BE THE LONGEST CARBON CHAIN IN OUR MOLECULE.
AND SO THIS GROUP OF NAMES ARE--
IS REFERRED TO AS THE HOMOLOGOUS SERIES.
AND IT WILL BE BUILDING ON THOSE GREEK PREFIXES
THAT YOU LEARNED WHEN YOU WERE LEARNING HOW TO NAME BINARY
COVALENT COMPOUNDS. ALL RIGHT.
SO LET'S LOOK AT IT MORE CLOSELY, RIGHT.
SO FOR THE ALKANE,
THIS WILL BE THE HYDROCARBON THAT HAS ALL SINGLE BONDS.
IF WE HAVE ONE CARBON PRESENT,
IT'S REFERRED TO AS METHANE.
AND IF IT'S A SUBSTITUENT OR A BRANCH,
THEN WE WOULD USE METHYL.
RIGHT? SO THE MAIN THING
ABOUT THE HOMOLOGOUS SERIES IS WE'RE LOOKING AT THESE PREFIXES.
THIS IS ABOUT THE PREFIXES.
ALL RIGHT.
SO WHEN WE SEE METH,
WE KNOW THAT WE ONLY HAVE ONE CARBON.
ETH, WOULD BE TWO CARBONS.
ALL RIGHT.
SO ETHANE IS WHEN IT'S THE PARENT AND THEN
IF IT'S A BRANCH COMING OFF OF A LONGER CHAIN,
IT WOULD BE ETHYL.
NOW, I'M GOING TO SWITCH TO A BOND-LINE STRUCTURES, RIGHT?
SO PROP, TELLS US WE HAVE THREE CARBONS. RIGHT?
SO THE END OF EVERY LINE AND EVERY CORNER IS A CARBON,
SO THERE WE GO. THERE'S OUR PROPANE.
AND IF IT WAS A BRANCH,
PROPYL, RIGHT? OKAY.
SO NOW, WE'RE JUST GOING TO MOVE ALONG THE SERIES.
BUTANE WOULD BE FOUR.
AND NOW WE'RE GOING TO SEE WHERE WE OVERLAP
WITH THOSE GREEK PREFIXES THAT WE LEARNED BEFORE. RIGHT?
PENTANE WILL BE FIVE CARBONS.
HEXANE WILL BE SIX. RIGHT?
AND THEN IF IT'S A BRANCH,
WE USE THE YL. RIGHT?
HEPTANE WOULD BE SEVEN.
OCTANE IS EIGHT.
LET ME SEE.
MAKE SURE I DID THAT ONE RIGHT, THREE, FOUR, FIVE,
SIX, SEVEN, EIGHT, PREFECT.
OKAY. NONANE IS NINE.
AND DECANE IS TEN.
ALL RIGHTY.
SO YOU SHOULD HAVE MOST OF THE HOMOLOGOUS SERIES
ALREADY MEMORIZED.
PENTANE, FIVE THROUGH TEN, YOU ALREADY KNOW.
THE NEW ONES ARE METH, ETH, PROP, AND BUT,
FOR ONE, TWO, THREE, AND FOUR.
PROPANE, THAT'S A BIG DEAL, RIGHT?
THAT'S THE BARBECUE GAS, RIGHT,
IF YOU HAVE A GAS BARBECUE,
AND BUTANE IS WHAT WE USE WITH LIGHTERS, OKAY?
AND METHANE, THAT'S MOSTLY FOUND IN FARTS, IN COW FARTS.
SO, ANYWAY, PUT A LITTLE PERSONALITY
ON THOSE SO THAT YOU CAN--
THEY MAY HAVE A LITTLE MORE MEANING PERHAPS.
OKAY. SO MAKE SURE, RIGHT,
TO MEMORIZE THE HOMOLOGOUS SERIES.
THE SOONER, THE BETTER.
NOW, THAT'S REALLY ALL THERE IS.
THAT'S THE KNOWLEDGE.
LET'S PRACTICE OUR WISDOM.
LET'S LOOK AT SOME HYDROCARBONS AND PRACTICE NAMING THEM.
ALL RIGHT.
SO THIS WOULD BE ANOTHER GOOD PLACE IN THE VIDEO TO HIT PAUSE
AND DO YOUR BEST TO NAME EACH OF THESE HYDROCARBONS.
AND HERE, THERE'LL BE THE PARENT AND THEN HERE,
WE'LL USE THE BRANCH NAME OR THE SUBSTITUENT NAME.
SO IF YOU WANT TO GO AHEAD AND PAUSE,
THAT WOULD BE AWESOME.
ALL RIGHTY. WELCOME BACK.
LET'S SEE HOW YOU DID. RIGHT?
SO ONE, TWO, THREE, FOUR, FIVE.
FIVE CARBONS.
THIS WOULD BE CALLED PENTANE.
ONE, TWO, THREE.
PROPANE. ALL RIGHT.
ONE, TWO, THREE, FOUR. BUTANE.
AND THEN AS WE'VE LEARNED, RIGHT,
THESE THINGS CAN WIGGLE ALL AROUND.
SO THEY MIGHT NOT ALWAYS HAVE THAT SAWTOOTH SHAPE
THAT WE EXPECT BUT THAT DOESN'T BOTHER US.
WE SEE THAT IT HAS SIX CARBONS. HEXANE.
HERE'S A NICE, BIG, LONG ONE.
ONE, TWO, THREE, FOUR, FIVE,
SIX, SEVEN, EIGHT. OCTANE.
NOW, THE OCTANE THAT-- FOR--
IN GASOLINE IS NOT ALWAYS THE PURE STRAIGHT CHAIN,
SOMETIMES THE EIGHT CARBONS COULD BRANCH OFF. OKAY.
AND THEN THE LAST ONE, ONE, TWO, THREE, FOUR, FIVE, SIX, SEVEN.
HEPTANE. ALL RIGHT.
SO PRETTY STRAIGHTFORWARD.
AND NOW, TO PRACTICE USING THE HOMOLOGOUS SERIES
AS BRANCHES OR SUBSTITUENTS, WE LOOK HERE.
SO BENZENE, I'VE ATTACHED ALL OF THESE TO BENZENE.
SO THIS IS BENZENE RIGHT HERE.
IT'S A SIX-MEMBERED RING WITH ALTERNATING DOUBLE BONDS,
OR WE COULD ALSO WRITE IT THIS WAY,
OR WE COULD SIMPLY WRITE IT WITH A CIRCLE IN THE CENTER.
ALL RIGHT? BUT FOR THIS QUESTION,
WE ARE GOING TO FOCUS ON THESE BRANCHES.
ALL RIGHT? THESE ARE ALKYL,
OOPS, SLIDE THAT UP, ALKYL BRANCHES.
OKAY. SO FOR THIS,
RIGHT, THERE'S ONE, TWO.
THERE'S TWO CARBONS.
SO NOW, WE WOULD CALL THIS ETHYL.
RIGHT? WE CHANGE TO THE YL ENDING.
OKAY? WHEN IT WAS THE PARENT,
THEN WE HAD THE ANE ENDING. ALL RIGHT.
BUT AS BRANCHES, ALL RIGHT, SO THEN HERE, RIGHT,
THERE'S JUST ONE CARBON ON THE BRANCH,
SO WE WOULD DESCRIBE THAT AS A METHYL BRANCH.
ONE, TWO, THREE, FOUR, FIVE, RIGHT.
SO THEN THIS WOULD BE A PENTYL BRANCH.
THEN ONE, TWO, THREE, PROPYL.
ALL RIGHT. OKAY.
SO WE'RE JUST FOCUSING ON NAMING THE BRANCHES.
THIS WASN'T THE FULL COMPOUND NAME.
IT WOULD BE VERY SIMPLE TO GIVE THE ENTIRE NAME NOW.
SO SINCE WE'RE HERE, WE MIGHT AS WELL, RIGHT?
THIS WOULD BE ETHYLBENZENE, METHYLBENZENE,
WHICH NOBODY CALLS IT THAT.
THEY CALL IT TOLUENE. RIGHT.
AND THEN PENTYLBENZENE, PROPYLBENZENE.
ALL RIGHTY. OKAY.
SO, THERE IS A BRIEF INTRODUCTION
TO THE HOMOLOGOUS SERIES.
YOU WANT TO GO AHEAD AND TAKE ADVANTAGE OF THAT GOOD WORK
YOU DID WITH GREEK PREFIXES
AND MEMORIZE THE LAST OF THE HOMOLOGOUS SERIES
SO YOU'LL BE READY TO DO HOMEWORK.