- WELCOME TO CARBOHYDRATES PART TWO.
WE'LL TAKE A QUICK CLOSER LOOK AT MONOSACCHARIDES
AND REVIEW THE IDEA OF CHIRALITY
THAT WAS FIRST INTRODUCED WITH AMINO ACIDS.
LET'S GO AHEAD AND LOOK AT GLYCERALDEHYDE,
ONE OF THE SIMPLEST SUGARS, RIGHT?
SO, IF WE LOOK HERE,
IT'S A VERY SIMPLE THREE CARBON SUGAR.
THE ALDEHYDE AT THE TOP,
AND THEN, WE SEE THE ALCOHOL ON THE RIGHT,
AND THEN, THE TERMINAL ALCOHOL.
SO, WE REMEMBER FROM AMINO ACIDS
THAT WHEN WE HAVE THE HORIZONTALS
THOSE REPRESENT THE WEDGES POKING OUT AT US.
AND THE VERTICAL AXIS
WOULD BE THE DASHES GOING BACK INTO THE PAPER.
AND SO, THAT'S DRAWN HERE AS WELL.
AND SO, THIS WOULD BE THE D-GLYCERALDEHYDE.
NOW, WE CAN MAKE--
RIGHT, THERE'S THE MIRROR PLANE, WE CAN DO THE MIRROR IMAGE.
SO, NOW WE HAVE THE TWO MIRROR IMAGES.
SO, WHAT IS THE RELATIONSHIP THAT WE USE TO DESCRIBE THOSE?
REMEMBER, WE CALL THEM ENANTIOMERS.
AND SO, NOW, I WANTED TO USE SOME MODELS
TO HELP ILLUSTRATE THIS IDEA.
SO, REMEMBER ENANTIOMERS COME IF WE HAVE A CHIRAL CARBON.
AND THE CHIRAL CARBON--
RIGHT, IT HAS A TETRAHEDRAL CARBON
AND BOND INTO FOUR DIFFERENT GROUPS,
FOUR DIFFERENT GROUPS, RIGHT?
SO, WE CAN SEE THAT WE HAVE THE HYDROGEN, A CH2OH,
AN OH, AND AN ALDEHYDE.
SO, WE DEFINITELY HAVE FOUR DIFFERENT GROUPS.
SO, LET'S START WITH A VERY SIMPLE MODEL.
AND THEN, WORK OUR WAY UP TO GLYCERALDEHYDE.
SO, I'LL PUT A LITTLE COVER HERE.
AND THEN, WE'LL LOOK AT THE TWO MODELS.
ALL RIGHT.
SO, IF WE LOOK AT THESE, WE CAN SEE,
IF WE LOOK FROM THE SIDE, RIGHT?
THAT WE HAVE THE MIRROR--
THEIR MIRROR IMAGES OF EACH OTHER,
HOWEVER, THE NON-SUPERIMPOSABLE.
IF I TRY TO OVERLAP, I CAN GET--
WE CAN GET THE PURPLE AND THE REDS TO OVERLAP,
BUT THEN NOTICE THAT THE BLUES
AND THE WHITES DON'T MATCH, OKAY?
OR, IF I TRY TO--
IF I LINE UP THE BLUES AND WHITES,
THEN NOTICE THAT THE REDS AND PURPLES DON'T LINE UP.
ALL RIGHT?
SO, THIS IS CHIRALITY.
WE HAVE OUR TETRAHEDRAL CARBON.
AND IT'S BONDED TO FOUR DIFFERENT GROUPS SYMBOLIZED
BY THE FOUR DIFFERENT COLORS.
AND SO, THESE ARE REFERRED TO AS A PAIR OF ENANTIOMERS.
NOW, WE'LL LOOK AT THE GLYCERALDEHYDE.
ALL RIGHT.
SO, HERE WE SEE-- RIGHT, THERE'S THE--
HERE IS THE CHIRAL CARBON BONDED TO THE FOUR DIFFERENT GROUPS.
SO, WE HAVE THE HYDROGEN,
AND THE METHYL GROUP WITH THE OH,
AND THE ALCOHOL GROUP, AND THE ALDEHYDE.
SO, NOW, IF I BRING IN THE OTHER ENANTIOMER, RIGHT?
SO, NOW, WE CAN SEE THEY ARE MIRROR IMAGES. SEE?
THERE'S THE TWO ALCOHOL GROUPS AND THE HYDROGENS.
UP AT THE TOP WE HAVE THE--
OOPS, THE ALDEHYDES.
THIS IS TRICKY. AND THEN,
WE HAVE OUR ALCOHOL GROUPS.
SO, THIS WOULD BE A PAIR OF ENANTIOMERS,
NON-SUPERIMPOSABLE MIRROR IMAGES.
AND SO, WE CAN SEE THE ALCOHOL AND THE ALDEHYDES ARE LINED UP.
BUT THEN, THE HYDROGENS AND THESE OTHER ALCOHOLS WON'T.
SO, THEY'RE MIRROR IMAGES BUT THEY'RE NON-SUPERIMPOSABLE.
SO, THAT SHOWS US THAT THIS CARBON
IN THE CENTER IS CHIRAL. OKAY.
SO, LET'S GO BACK TO OUR NOTES NOW.
AND. SO, IF WE WANTED TO,
WE COULD STAR THAT THESE ARE CHIRAL CARBONS.
AND SO, WE WOULD DESCRIBE THIS AS OUR PAIR
OF ENANTIOMERS. OKAY.
SO NOW, LET'S LOOK AT SOME OF THOSE SUGARS
THAT WE WERE INTRODUCED TO IN THE LAST TUTORIAL, RIGHT?
GLUCOSE, GALACTOSE, FRUCTOSE,
AND RIBOSE AND LET'S APPLY OUR KNOWLEDGE OF CHIRALITY.
SO, WE CAN SEE THAT SUGARS HAVE A TON OF CHIRAL CARBONS, RIGHT?
WE CAN STAR THEM.
THE KETOSIS TEND TO HAVE ONE LESS
BECAUSE OF THE INTERNAL CARBONYL.
AND THEN, THERE'S THE RIBOSIS.
OKAY. SO, A LITTLE BIT OF REVIEW,
REMEMBER, THE ENANTIOMERS ARE
THE NON-SUPERIMPOSABLE MIRROR IMAGES, RIGHT?
AND THAT COMES FROM HAVING CHIRAL CARBONS.
BUT WHAT HAPPENS WHEN WE HAVE SO MANY CHIRAL CARBONS?
WELL, THAT CREATES THE POSSIBILITY
OF A DIASTEREOMER.
SO, THESE ARE NON-SUPERIMPOSABLE STEREOISOMERS
THAT ARE NOT MIRROR IMAGES.
SO, LET'S LOOK AT THESE TWO TERMS AND COMPARE
THEM TO THESE VARIOUS SUGARS WE'RE LEARNING ABOUT.
ALL RIGHT?
SO, FIRST LET US LOOK AT THE WORD ENANTIOMERS.
SO, WHEN WE LOOK AT D-FRUCTOSE AND L-FRUCTOSE.
IF WE LOOK RIGHT HERE, NOTICE,
RIGHT, THAT IF WE PUT A MIRROR,
RIGHT, THAT--
WE'LL LOOK HERE, RIGHT?
SO, THERE WE HAVE THE REFLECTION,
AND THE REFLECTION, AND THE REFLECTION.
AND THEN, THIS COULD ROTATE, SO WE COULD MAKE IT PERFECT.
BUT, WE'RE REALLY FOCUSING ONLY ON THE CHIRAL CARBONS,
SO WE SEE FOR ALL OF THE CHIRAL CARBONS
THAT WE HAVE THE MIRROR IMAGE.
SO, THE RELATIONSHIP
BETWEEN D-FRUCTOSE AND L-FRUCTOSE THEN IS THAT THEY ARE
NON-SUPERIMPOSABLE MIRROR IMAGES.
THEY ARE A PAIR OF ENANTIOMERS.
SO, NOW, WE'LL LOOK AT AN EXAMPLE
OF THE TERM DIASTEREOMER.
NOW, LET'S COMPARE GLUCOSE TO GALACTOSE.
AND REMEMBERING THAT THE TERMS ENANTIOMERS
AND DIASTEREOMER HAVE TO DO WITH CHIRAL CARBONS.
SO, WE'RE JUST LOOKING AT THE CHIRAL CARBONS.
SO, NOW, WHEN WE LOOK AT GLUCOSE AND GALACTOSE
WE SEE-- WAIT A MINUTE.
THESE TWO ARE THE SAME, MIRROR, SAME, SAME.
ALL RIGHT? SO, IT'S--
ARE NOT IDENTICAL AND THEY'RE NOT
THE FULL MIRROR IMAGE LIKE WE SAW HERE WITH FRUCTOSE.
SO, GLUCOSE AND GALACTOSE,
THEY'RE AN EXAMPLE OF DIASTEREOMERS
WHERE WE HAVE MORE THAN ONE CHIRAL CARBON, RIGHT?
SO, IF THEY'RE ALL REVERSED, IF THEY'RE ALL MIRROR IMAGES,
WE SAY THEY'RE ENANTIOMERS.
BUT, IF ONLY SOME OF THEM ARE MIRROR IMAGES
AND SOME OF THEM ARE IDENTICAL,
WE CALL THEM DIASTEREOMERS, RIGHT?
SO, THIS IS TWO TYPES OF STEREOISOMERS.
AND THEN, LET'S REMIND OURSELVES,
WHAT WOULD BE THE BEST TERM TO DESCRIBE THE RELATIONSHIP
BETWEEN D-GLUCOSE AND D-FRUCTOSE?
WELL, AND FROM ONE OF OUR EARLIER TUTORIALS,
WE REALIZED THAT THEY BOTH HAVE THE CHEMICAL FORMULA C6H12O6.
BUT THEY HAVE VERY DIFFERENT CONNECTIONS,
SO THEY ARE STRUCTURAL OR CONSTITUTIONAL ISOMERS.
SO, WE HAVE AN EXAMPLE OF STEREOISOMERS
AND STRUCTURAL ISOMERS,
AND THE SUGARS. ALL RIGHTY.
SO, THAT CONCLUDES OUR TUTORIAL
ON THE CHIRALITY OF MONOSACCHARIDES.
TAKE TIME NOW TO WORK A FEW HOMEWORK PROBLEMS
TO REINFORCE YOUR UNDERSTANDING.