Functional Groups Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings 1

Functional groups are a characteristic feature of organic molecules that behave in a predictable, similar way. composed of an atom or group of atoms. groups that replace a hydrogen atom in the corresponding alkane. a way to classify families of organic compounds. Functional Groups 2

Alkenes and Alkynes Alkenes contain a double bond between adjacent carbon atoms. (Double bond: 4 electrons) Alkynes contain a triple bond. (Triple bond: 6 electrons) Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings 3

OH - vs -OH OH - : hydroxide anion found in bases (e.g NaOH) -OH: hydroxyl group colvalently bound to carbon atom in an organic compound (e.g. ethanol CH3-CH2OH) 4

2. Ethers In an ether, an oxygen atom is bonded to two carbon atoms. –C–O–C–. has a common name that gives the alkyl names of the attached groups followed by ether. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings 5 Diethyl ether

3. Aldehydes An aldehyde contains a carbonyl group (C=O), which is a carbon atom with a double bond to an oxygen atom. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings 6 acetaldehyde formaldehyde

4. Ketones In a ketone, the carbon of the carbonyl group is attached to two other carbon atoms. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings 7 Acetone

5. Carboxylic Acids and Esters Carboxylic acids contain the carboxyl group, which is a carbonyl group attached to a hydroxyl group. O ║ — C—OH Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings 8 Acetic acid

5. Esters An ester contains the carboxyl group between carbon atoms. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings 9 Methyl acetate

Organic compounds with Carbon- Nitrogen bonds 1. Amines In amines, the functional group is a nitrogen atom. H H C —N – H or C —N —C Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings 10 Methyl amine Dimethyl amine

Naming simple amines Simple 1º amines are named as “alkylamine” –Examples: methylamine CH 3 NH 2 ethylamine CH 3 CH 2 NH 2 butylamine CH 3 CH 2 CH 2 CH 2 NH 2 Symmetrical 2º or 3º amines are named as “dialkylamine” or “trialkyamine ” –Examples : diethylamine (CH 3 CH 2 ) 2 NH; trimethylamine (CH 3 ) 3 N

Examples: Amines are much more polar, than hydrocarbons, especially in acidic conditions

Heterocyclic amines Some amines have a nitrogen as part of a ring. These generally have common (non-systematic) names: anilinepyridinepyrimidine pyrrole quinolineindole imidazolebenzimidazole

Properties of amines Amines are moderately polar and are capable of hydrogen bonding. Low MW amines (up to about C 5 ) are soluble in water; higher MW amines will dissolve in acidic solution (as their conjugate acid). Many amines have foul odors. Amines are weak bases.

Example of biologically active amines

More biologically active amines…

Learning Check Classify each of the following as: alcohol, ether, aldehyde, ketone, carboxylic acid, ester, amine or amide. 1)CH 3 ─CH 2 ─CH 2 ─OH 2) CH 3 ─O─CH 2 ─CH 3 3) CH 3 ─CH 2 ─NH 2 O O ║ ║ 4) CH 3 ─C─OH 5) CH 3 ─C─O─CH 3 alcohol ether amine carboxylic acid ester 18

Organic compounds with Carbon-Oxygen bonds 1. Alcohols An alcohol contains the hydroxyl (-OH) functional group. (instead of an H in that place) Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings Ethanol

Alcohols An alcohol contains a hydroxyl group (—OH) attached to a carbon chain. A phenol contains a hydroxyl group (—OH) attached to a benzene ring. water alcohol phenol Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings 20

Naming Alcohols The names of alcohols in IUPAC replace the -e with -ol. with common names use the name of the alkyl group followed by alcohol. FormulaIUPACCommon Name CH 4 methane CH 3 ─OH methanol methyl alcohol CH 3 ─CH 3 ethane CH 3 ─CH 2 ─OH ethanol ethyl alcohol 21

Classification of alcohols is determined by the number of alkyl groups attached to the carbon bonded to the hydroxyl. primary (1°), secondary (2°), or tertiary(3). Primary (1º) Secondary (2º) Tertiary (3º) 1 group 2 groups 3 groups H CH 3 CH 3 | | | CH 3 —C—OH CH 3 —C—OH CH 3 —C—OH | | | H H CH 3 Classification of Alcohols 22

Properties of Alcohols and Ethers Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings 23

Boiling Points of Alcohols Alcohols contain polar OH groups. form hydrogen bonds with other alcohol molecules. have higher boiling points than alkanes and ethers of similar mass. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings 24

Boiling Points of Ethers Ethers do not have a polar group. have an O atom, but there is no H attached. cannot form hydrogen bonds between ether molecules. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings 25

Solubility of Alcohols and Ethers in Water Alcohols and ethers are more soluble in water than alkanes because the oxygen atom can hydrogen bond with water. 26

Comparing Solubility and Boiling Points Molar Boiling Soluble Compound Mass Point (°C) in Water? Alkane CH 3 ─CH 2 ─CH No Ether CH 3 ─O─CH Yes Alcohol CH 3 ─CH 2 ─OH 4678 Yes 27