ALDEHYDES AND KETONES ALDEHYDES CARBONYL GROUP A FUNCTIONAL

ALDEHYDES AND KETONES

ALDEHYDES • CARBONYL GROUP – A FUNCTIONAL GROUP THAT HAS A CARBON JOINED TO AN OXYGEN ATOM BY A DOUBLE BOND (C=O) • ALDEHYDES – COMPOUNDS THAT HAVE A CARBONYL GROUP BONDED TO ONE CARBON AND TO ONE HYDROGEN. THE CARBONYL GROUP OF AN ALDEHYDE IS OFTEN ABBREVIATED AS –CHO. DO NOT CONFUSE THIS SYMBOL WITH THAT OF AN ALCOHOL.

NAMING ALDEHYDES • ALDEHYDES ARE NAMED BY REPLACING THE FINAL “E” OF THE NAME OF THE ALKANE WITH THE SAME NUMBER OF CARBONS TO “AL”. • BECAUSE IN ALDEHYDES THE CARBONYL GROUP IS ALWAYS ATTACHED TO THE FIRST CARBON, THERE IS NO NEED TO PLACE A 1 IN FRONT OF THE NAME. • IF THERE ARE SUBSTITUENTS PRESENT, THE CHAIN IS NUMBERED BEGINNING WITH 1 FOR THE CARBON ATOM AT THE –CHO AND THE NAMES ARE LISTED ALPHABETICALLY. IF THERE ARE TWO OR MORE IDENTICAL BRANCHES, USE PREFIXES.

ALDEHYDES • EXAMPLES:

ALDEHYDES • EXAMPLES: HEXANAL 4 -METHYLHEPTANAL

KETONES • KETONES – COMPOUNDS THAT HAVE A CARBONYL GROUP BONDED TO TWO CARBONS. • SO, BOTH ALDEHYDES AND KETONE CONTAIN A CARBONYL GROUP. THE DIFFERENCE BETWEEN THEM IS THAT IN THE ALDEHYDE THE CARBONYL GROUP IS AT THE END OF THE CHAIN AND IN THE KETONE THE CARBONYL GROUP IS IN A SECONDARY CARBON.

NAMING KETONES • THE LONGEST CHAIN MUST CONTAIN THE CARBONYL GROUP AND THE PARENT NAME WILL END IN “ONE”. • NUMBER THE CHAIN IN THE DIRECTION THAT GIVES THE CARBONYL GROUP THE LOWEST POSSIBLE NUMBER AND PLACE THE NUMBER OF THE CARBON WITH THE CARBONYL GROUP IN FRONT OF THE NAME. • AS WITH OTHER COMPOUNDS, DENOTE THE LOCATION AND NAME OF EACH BRANCH IN ALPHABETICAL ORDER, AND IF THERE ARE TWO OR MORE IDENTICAL BRANCHES USE PREFIXES.

KETONES • EXAMPLES:

KETONES • EXAMPLES: • 3, 3 -DIBROMO-2 -PENTANONE • 4, 5 -DIMETHYL-2 -HEXANONE

PROPERTIES OF ALDEHYDES AND KETONES • THE POLARITY OF THE CARBONYL GROUP MAKES ALDEHYDES AND KETONES MODERATELY POLAR COMPOUNDS. AS A RESULT, THE HAVE HIGHER BOILING POINTS THAN ALKANES WITH SIMILAR MOLECULAR WEIGHTS. HOWEVER, BECAUSE THEY DON’T HYDROGEN BOND WITH EACH OTHER, THEY HAVE LOWER BOILING POINTS THAT ALCOHOLS. • IN A SERIES OF COMPOUNDS OF SIMILAR MOLECULAR WEIGHTS, THEIR BOILING POINTS ARE AS FOLLOWS: • ALKANES < ALDEHYDES/KETONES < ALCOHOLS • ALDEHYDES AND KETONES ARE SOLUBLE IN ORGANIC SOLVENTS, AND THOSE WITH FEWER THAN FIVE CARBONS ARE ALSO SOLUBLE IN WATER, BECAUSE THEY ARE ABLE TO HYDROGEN BOND WITH WATER MOLECULES.

REACTIONS OF ALDEHYDES AND KETONES • OXIDATION OF ALDEHYDES - AS PREVIOUSLY MENTIONED, ALDEHYDES CAN BE OXIDIZED TO CARBOXYLIC ACIDS.

REACTIONS OF ALDEHYDES AND KETONES • OXIDATION OF KETONES- KETONES ARE RESISTANT TO OXIDATION. NO REACTION

REACTIONS OF ALDEHYDES AND KETONES • REDUCTION REACTIONS – THE SYMBOL USED FOR A REDUCING AGENT IS [H]. A REDUCING AGENT SUCH AS H 2 IN THE PRESENCE OF A CATALYST SUCH AS Ni OR Pt CAN BE USED. A REDUCTION REACTION IS THE REVERSE OF AN OXIDATION. • REDUCTION OF ALDEHYDES – WHEN AN ALDEHYDE IS REDUCED, HYDROGENS ARE ADDED TO PRODUCE A PRIMARY ALCOHOL.

REACTIONS OF ALDEHYDES AND KETONES • REDUCTION OF KETONES- WHEN A KETONE IS REDUCED, HYDROGENS ARE ADDED TO PRODUCE A SECONDARY ALCOHOL.

ETHERS • ETHERS ARE COMPOUNDS IN WHICH AN OXYGEN ATOM HAS TWO SINGLE BONDS TO TWO ALKYL GROUPS.

NAMING ETHERS • ETHERS ARE NAMED AS ALKOXY ALKANES • IDENTIFY THE PARTS ATTACHED TO THE OXYGEN. • THE SHORTER OF THE TWO CHAINS IS NAMED FIRST AND ITS ANE ENDING IS CHANGED TO OXY. • THE LONGER CHAIN NAMED SECOND AND IS NAMED AS AN ALKANE. METHOXYPROPANE METHOXYETHANE

NAMING ETHERS • ANOTHER SYSTEM FOR NAMING ETHERS WORKS BY CITING THE NAMES OF THE R GROUPS IN ALPHABETICAL ORDER, FOLLOWED BY THE NAME ETHER. • METHYL PROPYL ETHER DIETHYL ETHER