Hydrocarbon Derivatives Aldehydes, Ketones, Carboxylic Acids, & Esters

Functional Group #4 Aldehydes

Carbonyl Group >CO Oxygen attached to a carbon by a double covalent bond. Strong dipole

Aldehydes O General formula: RCH or RCHO Carbonyl group is always at the end of the aldehyde (C on one side, H on the other). Find the name of the alkane with the same # of carbons. Change the final e to -al. Never need #’s for aldehydes – always at end. 

O H = HCO H  HCH H Aldehyde comes from Alcohol Dehydrogenated

HCH O  Methanal Common name = formaldehyde O H HCCH  Ethanal = acetaldehyde 1 metabolic product of ethanol on its route to acetic acid.

Acetaldehyde Evidence that it is carcinogenic. Natural component of many ripe fruits. Contributes to odors of rosemary, daffodil, bitter orange, camphor, angelica, fennel, mustard, & peppermint. A component of cigarette smoke.

Ends in CHO so it’s an aldehyde. CH3CH2CH2CHO 4 Carbons so base name is butane. Drop final -e and add –al  butanal.

Properties of Aldehydes - O R H H R - -   + C=O C=O   + + H H Aldehydes are polar! Bumps up the boiling point. 1-way Hydrogen bonding in H2O. Bumps up solubility.

Functional Group #5 Ketones

Ketones Carbonyl group , >C=O, located within a C chain instead of at the end. General Format: R and R' may or may not be the same. O = RCR'

Naming Ketones Nearly always have a number. Take the corresponding alkane name. Drop final –e. Add –one. Number in front gives location of >C=O. (Lowest possible #.)

H O H HCCCH H H 2-propanone Common name = acetone O = CH3CH2CH2CCH3 2-pentanone

Aldehydes & Ketones Known for appealing tastes & smells. Used as flavorings in food & candy. Used as fragrances in perfumes. Vanilla & cinnamon = aldehydes

Properties of Aldehydes & Ketones Aldehydes & ketones contain C=O group, which makes the molecules polar. Boiling point: Higher than alkanes, lower than alcohols. In pure aldehydes & ketones, hydrogen bonding does NOT occur. No H bonded to O. Can have 1-way Hydrogen bonding in water, so they are pretty soluble in H2O.

Functional Group #6 Carboxylic Acids

Carboxylic Acids Carboxylic Acids are electrolytes! O Acidic H+ General Formula = RCOH Contains a carbonyl group & a hydroxyl group bonded to same C. The H is acidic. It ionizes in water! Carboxylic Acids are electrolytes! =

Ionization of Acetic Acid CH3COOH + H2O  CH3COO- + H3O+

Table R O = General Format: R-C-OH or R-COOH

Which of the following is an electrolyte? CH3OH CH3COOH CH2O C3H6O alcohol aldehyde ketone Correct answer is B, the carboxylic acid.

Which of the following is a nonelectrolyte? HCl CH3COOH NaOH CH3OH Correct answer is D, an alcohol.

Naming Carboxylic Acids Never need a number – functional group always at end. Find name of corresponding hydrocarbon. Drop final –e. Add the ending –oic + the word acid.

O = HCOH 1 C  methane. Methanoic acid Sting in red ants, bees O H HCCOH = Ethanoic Acid or Acetic acid 2 C  ethane

CH3CH2CH2CH2COOH 5 C’s  pentane so the name is pentanoic acid.

Common carboxylic acids Acetic acid – vinegar. Also produced in doughs leavened with a specific yeast  sourdough bread Citric acid Tannic acid Ascorbic acid Lactic acid Poly(lactic acid) – biodegradable polymers used as sutures in internal surgery.

Properties of Carboxylic Acids Contain –COOH group. H is bonded to O. Hydrogen bonding occurs. Leads to increases in boiling point over corresponding alkane. Also can form hydrogen bonds with water so the smaller acids are pretty soluble.

Functional Group #7 Esters

Esters O = General format: RCOR‘ R and R‘ = hydrocarbon branches. Can be the same or different. Esters contain a carbonyl group and a bridge O, both in the middle of the chain. Esters are POLAR, but NO H bonded to O however.

Esters O = RCOR‘ or RCOOR’ Combination of a carboxylic acid & an alcohol. The carbonyl group and “R” come from the carboxylic acid. The bridging O and the R’ come from the alcohol.

Esters Responsible for many distinctive odors Pineapple Banana Orange Wintergreen

Naming Esters Name the hydrocarbon branch bonded to the bridge O first. Branches end in –yl. The base name is derived from the branch containing the carbonyl group. Count up all the C atoms in this branch, including the C in the carbonyl. Find the hydrocarbon base name. Drop the final –e and add –oate.

O So you name this branch 1st. = CH3CH2COCH3 Carbonyl Group Bridge O Methyl Propanoate

Bridge O O = CH3CH2CH2COCH2CH3 Name this branch 1st. Ethyl Butanoate Pineapple

Bridge O O = CH3COCH2CH2CH2CH2CH3 Name this branch 1st. Pentyl Ethanoate Banana

O = CH3OCCH2CH2CH3 Bridge O Name this branch 1st. 4 C’s on the other side = but Methyl butanoate - apple

O = CH3CH2CH2CH2CH2CH2CH2CH2-O-C-CH3 Bridge O Name this branch 1st. 2 C’s on the other side: ethane Octyl Ethanoate orange