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Unformatted text preview: 13-1CarbohydratesCarbohydrates•CarbohydrateCarbohydrate::a polyhydroxyaldehyde, polyhydroxyketone, or substance that gives these compounds on hydrolysis•MonosaccharideMonosaccharide::a carbohydrate that cannot be hydrolyzed to a simpler carbohydrate•they have the general formula C HO , where n varies from 3 to 8•aldosealdose: a monosaccharide containing an aldehyde group•ketoseketose: a monosaccharide containing a ketone group13-2MonosaccharidesMonosaccharides•Monosaccharides are classified by their number of carbon atomshexoseheptoseoctosetriosetetrosepentoseFormulaNameC3H6O3C4H8O4C5H1 0O5C6H1 2O6C7H1 4O7C8H1 6O813-3MonosaccharidesMonosaccharides•There are only two triosesDihydroxyacetone (a ketotriose)Glyceraldehyde (an aldotriose)CHOCHOHCH2OHCH2OHC= OCH2OH13-4MonosaccharidesMonosaccharides•Glyceraldehyde contains a stereocenter and exists as a pair of enantiomersL-GlyceraldehydeD-GlyceraldehydeCHOCCHOCHOHCH2OHCH2OHHHO13-5Fischer ProjectionsFischer Projections•Fischer projectionFischer projection::a two dimensional representation for showing the configuration of tetrahedral stereocenters•horizontal lines represent bonds projecting forward •vertical lines represent bonds projecting to the rear•the carbon atom at the intersection of the horizontal and vertical lines is not shownD-GlyceraldehydeCHOCHOHCH2OHD-Glyceraldehydeconvert to a FischerprojectionHOHCHOCH2OH13-6D,L MonosaccharidesD,L Monosaccharides•According to the conventions proposed by Fischer•D-monosaccharideD-monosaccharide: a monosaccharide that, when written as a Fischer projection, has the -OH on its next to last carbon on the right•L-monosaccharideL-monosaccharide: a monosaccharide that, when written as a Fischer projection, has the -OH on its next to last carbon on the left13-7The four aldotetrosesThe four aldotetroses•...
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lecture4 -...

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