- WELCOME TO HYDROCARBONS PART 1.
THIS VIDEO TUTORIAL IS GOING TO FOCUS
ON THE STRUCTURAL FORMULAS,
REVIEWING HOW TO CONVERT FROM A LEWIS STRUCTURE
TO A SKELETAL LINE OR BOND-LINE STRUCTURE
TO A CONDENSED STRUCTURE AND VICE VERSA.
LET'S GET STARTED.
SO, HERE ARE THE THREE MAIN TYPES OF STRUCTURAL FORMULAS.
SO REMEMBER, THIS IS WHERE WE'VE STARTED WITH A LEWIS STRUCTURE,
WE SHOW, RIGHT, WE SHOW ALL OF THE ATOMS,
WE SHOW ALL OF THE BONDS,
AND WE REMEMBER TO SHOW THE LONE PAIR ELECTRONS.
ALL RIGHTY.
NOW, THIS GETS TO BE TOO MUCH INFORMATION
SO WE WANT TO ABBREVIATE IT.
SO TO ABBREVIATE IT, WE CAN USE THE SKELETAL LINE STRUCTURE.
AND HERE, WE WILL SIMPLY SHOW THE CARBON TO CARBON BONDS
AND THEN WE WILL SHOW THE HETEROATOMS
OF THE FUNCTIONAL GROUPS.
NOW, WHEN WE ARE WRITING FUNCTIONAL GROUPS,
WE WILL INCLUDE THE HYDROGENS.
AND THEN THE OPPOSITE OF A SKELETAL LINE STRUCTURE
WHERE WE'RE FOCUSING ON THE BONDING,
WE WILL LOOK AT THE CONDENSED STRUCTURE
AND THIS IS WHERE WE ALL LOOK AT ATOMS ONLY.
ALL RIGHTY. SO LET'S START WITH WHERE WE'RE FAMILIAR.
SO, IF WE WERE TO DO THE LEWIS STRUCTURE FOR THE COMPOUND--
THIS COMPOUND HERE, THIS WILL BE BUTANAL.
WE ARE SHOWING EVERY CARBON ATOM, EVERY HYDROGEN ATOM,
EVERY BOND, AND THEN WHEN WE SEE OXYGEN,
WE RECOGNIZE THAT WE HAVE TWO LONE PAIRS.
ALL RIGHT.
SO THIS WOULD BE THE EXPANDED STRUCTURAL FORMULA
OR THE LEWIS STRUCTURE.
NOW, ONCE WE GET FAMILIAR WITH ORGANIC COMPOUNDS,
THEN WE WANT TO DO ABBREVIATIONS.
SO, IF WE TOOK THE SAME COMPOUND
AND WE SHOWED IN ITS SKELETAL LINE STRUCTURE,
I'LL SLIDE THIS DOWN, OKAY, WE WOULD ABBREVIATE IT LIKE THIS.
SO EACH OF THESE--EACH OF THE CORNERS REPRESENTS A CARBON
AND THEN THERE'S OUR ALDEHYDE FUNCTIONAL GROUP.
IF WE WANTED TO SHOW THE SAME COMPOUND
USING A CONDENSED FORMULA,
WE WOULD TAKE ADVANTAGE OF THE FACT
THAT HERE'S OUR FIRST CARBON ATOM
AND THEN WE KNOW IT'S BONDED TO THREE HYDROGENS
AND THEN OUR SECOND CARBON ATOM IS BONDED TO TWO HYDROGENS
AND THEN WE KEEP FOLLOWING THE PROCESS,
AND WHEN WE GET TO OUR FUNCTIONAL GROUP HERE,
THERE'S THE CARBON, WE ALWAYS-- IF THE--
IF THERE'S A HYDROGEN BONDED TO THE CARBON,
IT'S ALWAYS LISTED FIRST AND THEN WE WOULD LIST THE OXYGEN.
SO THE MAIN THING WITH CONDENSED STRUCTURES IS RECOGNIZING
THAT THE CARBONS ARE FORMING THE BACKBONE.
AND THEN NOTICE TOO THAT FOR THE SKELETAL LINE STRUCTURE
AND THE CONDENSED FORMULA,
WE DON'T WORRY ABOUT THE LONE PAIR ELECTRONS
UNLESS WE'RE ASKED THE QUESTION THAT'S VERY CLEAR
AND SAYS WE MUST SHOW THEM.
ALL RIGHTY. SO LET'S REVIEW SOME BONDING PATTERNS.
NOW, THESE ABBREVIATED STRUCTURAL FORMULAS
WITH SKELETAL LINE OR CONDENSED, THESE FORMULAS WORK
BECAUSE WE TAKE ADVANTAGE OF KNOWING
OUR NEUTRAL BONDING PATTERNS FOR ORGANIC COMPOUNDS.
SO FOR EXAMPLE, WHEN WE LOOK AT HYDROGEN,
WE KNOW THAT HYDROGEN IS GROUP ONE,
IT ONLY HAS ONE VALENCE ELECTRON
SO HYDROGEN ALWAYS WANTS TO HAVE ONLY ONE BOND.
WHEN WE COMPARE THIS, FOR EXAMPLE,
TO CARBON WHICH IS GROUP FOUR, WHEN WE LOOK AT CARBON,
WE RECOGNIZE CARBON HAS FOUR VALENCE ELECTRONS.
SO WHEN CARBON FORMS COMPOUNDS,
IT ALWAYS WANTS TO FORM FOUR BONDS.
OF COURSE CARBON DOESN'T CARE HOW IT GETS THOSE FOUR BONDS.
CARBON DOESN'T CARE IF IT HAS FOUR SINGLE BONDS,
TWO SINGLE BONDS AND A DOUBLE BOND,
OR A SINGLE BOND AND A TRIPLE BOND.
ALL CARBON CARES ABOUT IS THAT IT ALWAYS HAS FOUR BONDS.
NOW, LET'S LOOK AT ANOTHER IMPORTANT ATOM THAT WE'LL SEE
IN BIOLOGICAL MOLECULES, THAT'S NITROGEN.
NITROGEN IS GROUP FIVE,
SO NITROGEN HAS FIVE VALENCE ELECTRONS.
SO HYDROGEN ALREADY HAS TWO OF ITS ELECTRONS PAIRED
SO NITROGEN WANTS--ALWAYS HAS A LONE PAIR
AND THEN IT LIKES TO FORM THREE BONDS.
AND JUST LIKE CARBON,
NITROGEN DOESN'T CARE HOW IT GETS THOSE THREE BONDS.
IT JUST CARES THAT IT HAS THREE BONDS AND ONE LONE PAIR.
AND THEN LAST BUT NOT LEAST,
LET'S REMIND OURSELVES ABOUT OXYGEN
AND OXYGEN'S BONDING PATTERNS.
OXYGEN IS GROUP SIX, SO IT HAS SIX VALENCE ELECTRONS.
SO WHEN OXYGEN FORMS COMPOUNDS,
IT WILL HAVE TWO SETS OF LONE PAIRS AND TWO BONDS.
AND JUST LIKE CARBON AND NITROGEN,
OXYGEN DOESN'T CARE HOW IT GETS ITS TWO BONDS.
THEY COULD BE TWO SINGLE BONDS OR TWO DOUBLE BONDS.
AND THEN WE HAVE THE TWO LONE PAIRS.
SO, IT IS THROUGH THEIR ABBREVIATED STRUCTURAL FORMULAS
WHETHER IT'S SKELETAL LINE OR CONDENSED FORMULA,
TAKES ADVANTAGE OF THE FACT
THAT WE UNDERSTAND THESE BONDING PATTERNS.
LET'S GO TO THE NEXT PAGE.
NOW WE WILL REVIEW HOW TO DRAW A SKELETAL LINE STRUCTURE.
SO LET ME GET THIS CENTERED
AND WE'LL GET STARTED ON THIS NEXT PAGE.
ALL RIGHTY.
SO BECAUSE OF THE NATURAL BONDING PATTERN
OF THOSE TETRAHEDRAL BOND ANGLES,
THE CARBON ATOMS MAKE THIS SAWTOOTH, ZIGZAG SHAPE.
SO THE END OF EVERY LINE
AND EVERY CORNER CORRESPONDS TO A CARBON ATOM.
SO, IF WE COUNTED OUR CARBON ATOMS,
HERE IN OUR LEWIS STRUCTURE, WE SEE WE HAVE FIVE CARBON ATOMS.
SO THIS--THE END OF THIS LINE REPRESENTS CARBON ONE,
CARBON TWO, THREE, FOUR, FIVE.
SO THESE TWO, THIS IS OUR LEWIS STRUCTURE AND OUR SKELETAL LINE.
THEY'RE REPRESENTING THE SAME COMPOUND PENTANE. RIGHT.
SO WE'LL BRIEFLY REVIEW THE RULES, RIGHT.
SO ALL CARBON-CARBON SINGLE BONDS
ARE SHOWN AS A SINGLE LINE,
DOUBLE BONDS ARE SHOWN AS TWO PARALLEL LINES
AND TRIPLE BONDS AS THREE PARALLEL LINES.
SO FOR EXAMPLE IF WE ADDED A DOUBLE BOND OR A TRIPLE BOND
TO OUR COMPOUND,
LET'S SEE HERE, RIGHT, ONE, TWO, THREE, FOUR, FIVE,
ONE, TWO, THREE, FOUR, FIVE.
ALL RIGHT.
SO NOTICE THAT WE ALWAYS IGNORE THE CARBON ATOMS
BECAUSE THEY'RE REPRESENTED AS THE END OF THE LINE OR A CORNER.
AND LET'S SEE.
THE HETEROATOMS, IT'S IMPORTANT TO DRAW THOSE AND THAT WOULD BE,
FOR EXAMPLE, IF WE HAVE OXYGEN OR NITROGEN.
SO NOTICE IN OUR SKELETAL LINE STRUCTURE,
WE'RE NOT SHOWING THE HYDROGEN ATOMS
BECAUSE EVERYBODY KNOWS THAT CARBON WANTS TO FORM FOUR BONDS
AND SO ANY MISSING INFORMATION IS ASSUMED TO BE HYDROGEN.
HOWEVER, IT IS IMPORTANT TO SHOW HYDROGEN
WHEN WE HAVE FUNCTIONAL GROUPS.
SO FOR EXAMPLE IF WE ADDED AN ALCOHOL, RIGHT,
WE WOULD SHOW THE HYDROGEN ON THE ALCOHOL GROUP.
SO LET'S PRACTICE THIS A BIT.
WE HAVE SOME PRACTICE COMPOUNDS RIGHT HERE. ALL RIGHTY.
SO HERE, WE CAN SEE THE CARBONS ARE FORMING A SIX-MEMBERED RING.
AND THEN WE NOTICE THAT WE DO HAVE A DOUBLE BOND PRESENT
ON THE RIGHT SIDE.
SO WE HAVE THE LEWIS STRUCTURE AND THE SKELETAL LINE STRUCTURE.
NOW, HERE WE HAVE AN ALCOHOL.
WE HAVE ONE, TWO, THREE, FOUR.
WE HAVE A FOUR CARBON CHAIN
SO START WITH OUR BACKBONE, OUR FOUR CARBON CHAIN,
AND THEN WE NOTICE THAT COMING OFF THE SECOND CARBON,
WE HAVE THE ALCOHOL GROUP.
AND THEN LAST BUT NOT LEAST,
HERE WE HAVE ANOTHER SIX-MEMBERED RING
BUT WE HAVE THE NITROGEN ATOM PRESENT.
SO EACH CORNER REPRESENTS A CARBON
AND THEN WE SHOW THE DOUBLE BONDS.
AND THEN IF THE QUESTION ASKS,
WE CAN ALWAYS ADD THE LONE PAIRS,
REMEMBERING THAT A NEUTRAL OXYGEN WANTS
TWO LONE PAIRS AND NITROGEN,
A SINGLE LONE PAIR TO COMPLETE THE OCTET.
ALL RIGHTY. SO NOW, LET'S REVIEW CONDENSED FORMULAS. ALL RIGHT.
BECAUSE WE KNOW--WE RECOGNIZE
THAT THE CARBON ATOMS FORM THE BACKBONE,
IT'S REALLY COMMON TO ADMIT THOSE BONDS.
FOR A 300 SERIES CLASS,
IT'S VERY COMMON TO SHOW THE DOUBLE OR THE TRIPLE BONDS
SO YOU DON'T HAVE TO DO TOO MUCH INVESTIGATIVE WORK.
THE MAIN THING TO KEEP IN MIND WITH THE CONDENSED FORMULA
IS THAT WE HAVE OUR CARBON BACKBONE
SO WE RECOGNIZE OUR BONDING PATTERN
THAT THE CARBONS ARE ALL GOING TO BE BONDED TOGETHER.
SO THE CONVENTION OF THE CONDENSED FORMULA
THEN IS HERE'S OUR FIRST CARBON,
WE WOULD LIST ANY HYDROGENS BONDED TO THAT CARBON,
IF THERE WERE ANY OTHER FUNCTIONAL GROUPS OR BRANCHES,
THEY WOULD BE INCLUDED AS PARENTHESIS.
THEN WE WOULD GO TO OUR NEXT CARBON IN THE BACKBONE
AND WE WOULD LIST ANY HYDROGENS BONDED TO THAT CARBON
AND THEN ANY BRANCHES OR FUNCTIONAL GROUPS
WOULD BE IN PARENTHESIS.
AND SO WE WOULD CONTINUE BUILDING OUR CARBON CHAIN
WITH THE SAME PATTERN LISTING THE CARBON
AND THEN ALL OF THE ATOMS BONDED
UNTIL WE GET TO THE LAST CARBON ON THE RIGHT
AND THIS PATTERN CAN CONTINUE FOR AS LARGE AS THE MOLECULE IS.
SO THESE THREE STRUCTURES, RIGHT,
WE HAVE OUR LEWIS STRUCTURE, OUR CONDENSED FORMULA,
AND OUR SKELETAL LINE BOND-LINE STRUCTURE.
SO THESE ARE ALL REPRESENTING THE SAME COMPOUND.
SO RECOGNIZING, HERE'S OUR ONE, TWO, THREE,
THERE'S OUR FIVE CARBONS, OUR FIVE CARBONS,
AND OUR FIVE CARBONS.
SO, WE WILL-- SO LET'S PRACTICE THIS.
SO WE WILL TALK ABOUT AND DEFINE STRUCTURAL ISOMERS.
YOU SHOULD ALREADY KNOW STRUCTURAL ISOMERS
FROM YOUR NOTES
AND WE'LL REVIEW THAT IN THE HYDROCARBON PART TWO VIDEO,
RIGHT.
SO STRUCTURAL ISOMERS, HERE'S AN EXAMPLE,
ALL FIVE OF THESE COMPOUNDS, ALL HAVE THE CHEMICAL FORMULA C6H14
BUT WE SEE THAT BECAUSE OF THE VERSATILITY OF CARBON,
WE ARE ABLE TO CONNECT THOSE SIX CARBON ATOMS
IN VERY DIFFERENT ARRANGEMENTS.
SO WE JUST START.
SO THIS FIRST CARBON HERE, SINCE WE ONLY SEE ONE BOND,
WE KNOW IT MUST BE BONDED TO THREE OTHER HYDROGENS.
AND THEN NOTICE WE'RE GOING TO HAVE ONE, TWO, THREE, FOUR,
WE HAVE FOUR CARBONS IN THE CENTER, THEY'RE ALL THE SAME,
SO WE CAN'T SIMPLIFY AND SHOW
THAT THIS REPRESENTS THE 4CH2 GROUPS IN THE MIDDLE
AND THEN WERE TO THE TERMINAL CARBON ON THE END
AND SO THERE'S OUR CONDENSED FORMULA.
YOU'RE ALSO FREE TO WRITE THIS OUT FOUR TIMES,
IF YOU DON'T MIND.
ALL RIGHTY.
NOW LET'S LOOK AT THIS NEXT STRUCTURAL ISOMER OF C6H14.
NOW WE CAN REPRESENT THIS--WE CAN JUST FOCUS ON THE SKELETON
AND TREAT THIS AS A BRANCH.
SO LET'S DO IT THAT WAY FIRST.
SO HERE IS OUR TERMINAL CARBON CH3
AND THEN WE GET TO OUT--WE GET TO THIS CARBON WITH THE BRANCH,
SO SINCE CARBON WANTS FOUR BONDS,
WE RECOGNIZE THAT THERE'S A HYDROGEN THAT HASN'T BEEN SHOWN
AND THEN WE WOULD USE THE PARENTHESIS
TO SHOW THE CH3 GROUP COMING OFF RIGHT HERE.
AND THEN WE CONTINUE ALONG THE CARBON CHAIN CH2, CH2, CH3.
WITH THIS MOLECULE THOUGH, IT IS COMMON TO SEE
THE CONDENSED FORMULA WRITTEN SLIGHTLY DIFFERENTLY.
WE COULD CONSIDER BOTH OF THESE CARBONS OF BRANCH ON THIS CARBON
RIGHT HERE.
SO AN ALTERNATIVE WAY TO RATE THE CONDENSED FORMULA
FOR THIS COMPOUND WOULD BE TO PUT THE TWO CH3 GROUPS
AT THE BEGINNING
AND THEN WE WOULD GET TO THE CARBON WITH OUR ARROW CH
AND THEN WE WOULD CONTINUE AS WE DID BEFORE.
SO, THERE ARE NO OFFICIAL RULES ON CONDENSED FORMULA
SO YOU WANT TO BE COMFORTABLE DRAWING A CONDENSED FORMULA
OR READING A CONDENSED FORMULA,
EITHER WAY, THESE BOTH REPRESENT THE COMPOUND ABOVE.
ONCE THE BRANCH GETS INTO THE MIDDLE OF THE CHAIN,
IT'S MUCH MORE STRAIGHTFORWARD.
SO WE BEGIN WITH OUR FIRST CARBON CH3 AND THEN A CH2
AND THEN WE GET TO WHERE WE HAVE OUR BRANCH.
SO THIS CARBON ONLY SHOWS THREE BONDS
SO WE KNOW IT MUST HAVE A HYDROGEN
AND THEN THERE'S OUR BRANCH.
WE'LL SHOW THAT WITH PARENTHESIS
AND THEN WE CAN CONTINUE ON WITH OUR CARBON CHAIN,
THERE WE GO.
ALL RIGHTY. OKAY. LET'S KEEP WORKING OUR WAY.
NOW THIS ONE IN PARTICULAR,
THIS IS ANOTHER EXAMPLE WHERE WE HAVE TWO ALTERNATIVES.
WE CAN THINK OF THIS AS A--
OOPS, A FOUR CARBON PARENT WITH TWO ONE CARBON BRANCHES,
SO IF WE VIEW IT THIS WAY, WE WOULD WRITE CARBON ONE CH3
AND THEN WHEN WE GET TO CARBON TWO, RIGHT?
IT HAS FOUR BONDS, THERE ARE NO HYDROGENS.
WE WOULD DRAW CARBON TWO AND THEN WE WOULD INDICATE
THAT IT HAS TWO ONE CARBON METHYL BRANCHES.
AND THEN WE WOULD CONTINUE ALONG OUR CHAIN
TO CARBON THREE AND CARBON FOUR.
IT IS ALSO POSSIBLE TO VIEW THIS,
BEGINNING WITH CARBON TWO
AND VIEWING ALL THREE OF THESE CARBON BRANCHES.
SO YOU MAY SEE THIS COMPOUND WRITTEN THIS WAY
WITH THE THREE CARBON BRANCHES COMING OFF
OF THE CARBON WITH THE ARROW
AND THEN THAT WOULD LEAVE US WITH CH2, CH3 TO FINISH.
SO BOTH FORM--AND EACH OF THESE CASES, BOTH FORMS ARE CORRECT
AND YOU WANT TO BE ABLE TO RECOGNIZE THEM. ALL RIGHTY.
AND THEN THIS LAST STRUCTURAL ISOMER HERE,
WE CAN JUST CONTINUE THIS ONE
WHEN THE BRANCHES ARE TO THE INSIDE.
WE HAVE CH3 AND THEN WE GET TO CARBON TWO,
IT HAS ONE HYDROGEN AND THEN A BRANCH
AND THEN WE GET TO CARBON THREE, IT HAS ONE HYDROGEN
AND THEN ONE CARBON BRANCH AND THEN WE GET TO CARBON FOUR.
SO, CONDENSED FORMULAS ARE IMPORTANT ESPECIALLY ON EXAMS
BECAUSE A LOT OF TIMES PROFESSORS USE QUESTIONS
FROM A TEST BANK
AND OFTEN THE TEST BANK COMMUNICATES THE STRUCTURE
AS A CONDENSED FORMULA.
SO YOU WANT TO BE VERY COMFORTABLE.
NOW, LET'S DO A BRIEF REVIEW OF WHAT WE'VE JUST PRACTICED,
BEFORE YOU CAN GET STARTED ON YOUR HOMEWORK.
ALL RIGHTY.
SO, BASICALLY WE HAVE FOUR DIFFERENT WAYS
TO DESCRIBE ORGANIC COMPOUNDS.
THE FIRST ONE, THE MOLECULAR FORMULA
COULD ALSO BE THE CHEMICAL FORMULA
AND WE HAVEN'T REALLY TALKED ABOUT THIS IN THE VIDEO
AND THE REASON FOR THAT
IS BECAUSE THERE IS NO STRUCTURAL INFORMATION.
HOWEVER, SOMETIMES, AFTER WE'VE TALKED
ABOUT STRUCTURAL FORMULAS,
STUDENTS KIND OF GET CONFUSED WHEN THEY HEAR MOLECULAR
OR CHEMICAL FORMULA.
SO I WANTED TO REMIND YOU THAT THIS IS SIMPLY AN INVENTORY,
HOW MANY CARBONS?
HOW MANY HYDROGENS? HOW MANY OXYGENS?
ARE THERE NITROGENS PRESENT?
ARE THERE ANY PHOSPHOROUS ATOMS PRESENT? RIGHT?
SO, THERE'S NO STRUCTURAL INFORMATION,
BUT IT CAN STILL BE USEFUL INFORMATION.
NOW, THIS IS WHERE WE FOCUSED ON THIS VIDEO TUTORIAL, RIGHT?
LEWIS STRUCTURE OR EXPANDED SHOWS EVERYTHING,
ALL ATOMS, BONDS, AND LONE PAIRS,
THE BOND LINE OR SKELETAL LINE STRUCTURE,
REMEMBER ONLY SHOWS CARBON TO CARBON BONDS
AND THE ATOMS OF THE FUNCTIONAL GROUPS.
AND THEN LAST BUT NOT LEAST, WE HAVE THE CONDENSED FORMULA
WHICH IS BASICALLY ATOMS ONLY.
AND IT'S PERFECTLY OKAY AND I-- IN MY CLASS,
I WILL ALWAYS SHOW YOU ANY DOUBLE OR TRIPLE BONDS.
ALL RIGHTY.
SO NOW, LET'S TAKE SOME TIME TO CONVERT BACK AND FORTH.
ALL RIGHTY.
AND I--AND I-- THIS FIRST EXAMPLE,
I'VE ASKED YOU TO SHOW-- WE'VE SHOWN THE SKELETAL LINE
AND I'VE ASKED YOU TO DRAW THE THREE OTHER WAYS.
BUT FOR RING STRUCTURES, THERE'S NO CONDENSED FORMULA.
SO WE CAN SKIP THAT PART.
SO WE CAN DO THE LEWIS STRUCTURE THOUGH, RIGHT?
RECOGNIZING THAT THE CORNER OF EVERY LINE IS A CARBON ATOM
AND THEN WE SEE THAT WE HAVE A DOUBLE BOND
AND THEN WE HAVE A BOND TO OXYGEN
AND THEN THAT BONDS TO HYDROGEN.
OKAY. NOW IS WHERE OUR BONDING PATTERNS COME INTO PLAY.
WE KNOW ALL OF THE CARBONS WANT TO HAVE FOUR BONDS.
AS WE LOOK AT THIS CARBON HERE,
WE SEE THAT IT MUST BE BONDED TO ONE ADDITIONAL HYDROGEN,
JUST LIKE THIS CARBON.
THESE CARBONS, HOWEVER, ONLY HAVE TWO BONDS,
SO WE RECOGNIZED THAT THERE MUST BE TWO ADDITIONAL BONDS
TO HYDROGEN.
WHEN WE LOOK AT THIS CARBON RIGHT HERE ONE, TWO, THREE,
IT ONLY HAS THREE BONDS PRESENT
SO WE'RE GOING TO HAVE TO ADD ONE MORE HYDROGEN.
AND THEN LAST BUT NOT LEAST,
BECAUSE WE'VE BEEN ASKED TO INCLUDE LONE PAIRS
AND WE ALWAYS INCLUDE LONE PAIRS IN THE LEWIS STRUCTURE,
NOW, OUR MOLECULE IS COMPLETE.
SO SINCE WE CAN'T DO A CONDENSED FORMULA FOR THIS RING,
THE ONLY THING LEFT TO DO IS WRITE THE CHEMICAL FORMULA,
SO THAT WOULD BE C5H12-- OH, NO, NOT H12, H8O.
OKAY. ALL RIGHTY.
NOW, WITH CONDENSED FORMULAS, THIS WAS ALSO A GOOD OPPORTUNITY
TO REMIND YOU OF THE ONE TIME WE CAN SHOW A RING, RIGHT?
WHEN WE HAVE A COMPOUND LIKE THIS, A BENZENE RING,
THIS IS THE ONLY RING
THAT WE CAN SHOW A CONDENSED FORMULA FOR.
THIS WOULD BE C6H5W.
SO A LITTLE--SLIDE THAT A LITTLE BIT OF TIDBIT IN THERE FOR YOU.
ALL RIGHTY. SO, LET'S KEEP PRACTICING.
NOW, WE HAVE A CONDENSED FORMULA
SO WE CAN DRAW ALL THE OTHER FORMS.
I THINK THE LEWIS STRUCTURE IS THE ONE
WE'RE MOST FAMILIAR WITH.
SO WHEN IN DOUBT, CREATE THE LEWIS STRUCTURE.
AND THEN FROM THIS LEWIS STRUCTURE,
YOU CAN CONVERT TO THE OTHER FORMS.
HERE, WE HAVE A CHO, THAT'S THE CHO, THAT'S AN ALDEHYDE,
YOU'LL RECOGNIZE THAT VERY SOON.
WE'LL START WITH THAT, IT'S OUR FIRST CARBON
AND THEN WE NOTICE WE HAVE ONE, TWO MORE CARBONS IN OUR CHAIN
AND THEN WE NOTICE THAT WE HAVE TWO CARBONS COMING OFF
OF THIS CARBON WITH THE ARROW.
ALL RIGHTY. SO WE'VE CREATED OUR CARBON SKELETON.
NOW, WE TAKE ADVANTAGE OF OUR BONDING PATTERNS.
IF WE LOOK HERE THIS IS TELLING US
THAT THIS HYDROGEN IS BONDED TO CARBON
BECAUSE IT FOLLOWS DIRECTLY BEHIND.
SO THEN WE WOULD HAVE AN OXYGEN. LET'S KEEP GOING.
HERE, WE HAVE OUR CH2, SO WE PUT IN OUR TWO HYDROGENS
AND THEN WE HAVE OUR CARBON, IT HAS ONE HYDROGEN
AND THEN IT HAS THE TWO BRANCHES,
EACH OF THOSE BRANCHES HAVE AN ADDITIONAL THREE HYDROGENS.
OKAY.
SO NOW, WHAT'S LEFT, AS WE LOOK OVER HERE
AND THIS DOESN'T LOOK RIGHT,
WE KNOW CARBON WANTS TO HAVE FOUR BONDS
AND OXYGEN WANTS TO HAVE TWO BONDS AND TWO LONE PAIRS.
SO WE CAN FINISH OUR LEWIS STRUCTURE BUILDING
OFF OUR UNDERSTANDING OF THE BONDING PATTERNS.
NOW THAT WE HAVE THE LEWIS STRUCTURE,
WE CAN CREATE OUR SKELETAL LINE STRUCTURE,
SO BEGINNING WITH THIS ALDEHYDE GROUP HERE,
THIS FUNCTIONAL GROUP, THIS CORNER, RIGHT?
REPRESENTS THIS CARBON AND THEN HERE'S OUR CH2
AND THEN HERE'S OUR CARBON WITH THE TWO BRANCHES.
AND WE'LL GO AHEAD AND PUT OUR LONE PAIRS
SINCE THE DIRECTIONS ASKED US TO.
ALL RIGHT.
SO WE HAD OUR CONDENSED FORMULA, OUR LEWIS STRUCTURE,
OUR SKELETAL LINE AND NOW WE SIMPLY ADD UP THE ATOMS
AND IT WOULD BE C5H10O AS THE CHEMICAL FORMULA.
ONE LAST BIT OF PRACTICE
BEFORE YOU GET STARTED ON YOUR HOMEWORK.
NOW, WE HAVE THE FULL LEWIS STRUCTURE.
SO THIS IS-- BE VERY STRAIGHTFORWARD.
LET'S DO THE CONDENSED STRUCTURE FIRST.
WE'LL START WITH THIS CARBON ATOM HERE.
WE SEE WE HAVE CH3 AND THEN WE COME HERE
AND THIS CARBON IS ONLY BONDED TO ONE HYDROGEN
AND WE'LL GO AHEAD AND SHOW EVERYBODY THE DOUBLE BOND
AND NOW WE'VE GOT INTO THE NEXT CARBON.
AND NOW WE HAVE NH2.
SO THIS LEWIS STRUCTURE, RIGHT?
NITROGEN THREE BONDS AND ONE LONE PAIR.
IF WE WANTED TO CONVERT THIS
INTO THE SKELETAL LINE STRUCTURE, VERY STRAIGHTFORWARD.
THERE WE ARE.
AND THEN LAST BUT NOT LEAST,
THE CHEMICAL FORMULA OR MOLECULAR FORMULA
WOULD BE C3H7 NITROGEN.
ALL RIGHTY.
SO, I HOPE THAT YOU HAVE FOUND THIS REVIEW
OF STRUCTURAL FORMULAS HELPFUL.
PLEASE TAKE SOME TIME NOW TO WORK A FEW HOMEWORK PROBLEMS
TO REINFORCE YOUR UNDERSTANDING.