FUNCTIONAL GROUPS IN ORGANIC COMPOUNDS

Naturally occurring organic compounds are found in plants, animals, and fossil fuels All of these have a plant origin All of these rely on the “fixing” of C from CO 2 ORIGIN OF ORGANIC COMPOUNDS ORIGIN OF ORGANIC COMPOUNDS

Most current research focuses on Organic Originally from “organic” meaning life Not just chemistry of life, chemistry of carbon Exceptions: –oxides of carbon (CO 2, CO) –carbonates,bicarbonates(NaHCO 3,CaCO 3 ) –cyanides (NaCN, etc) INTRODUCTION CCCCC One C with no H, or with metal Carbon can form four bonds…

Carbon can form four bonds, and forms strong covalent bonds with other elements This can be represented in many ways … CARBON FORMS FOUR BONDS CARBON FORMS FOUR BONDS

We already know this….. Hydrocarbons are compounds made up of only the elements carbon and hydrogen.

HYDROCARBONS HYDROCARBONS C AlkanesAlkenes AlkynesAromatics

New info… Cycloalkane – ring structure, all single bonds – Cyclohexane is one example Cycloalkene – ring structure, at least one double bond – Benzene is one example WE HAVE LEARNED ABOUT ALKANES, ALKENES, ALKYNES….

8 Aromatic hydrocarbons are so named because many of the earliest known aromatic compounds had strong characteristic odors. The simplest aromatic hydrocarbon is benzene. The six- membered ring and three  bonds of benzene comprise a single functional group. When a benzene ring is bonded to another group, it is called a phenyl group.

A functional group is – an atom or a group of atoms with characteristic chemical and physical properties. Types of atoms include oxygen, chlorine, oxygen attached to other hydrogens and carbons, etc. It is the reactive part of the molecule. OTHER ATOMS CAN ‘JOIN IN’ AND REPLACE ONE OR MORE H ATOMS

10 There are many types of functional groups….

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Alcohol R – OH Ether R – O – R Carboxylic acid R – CO – O – H Ester R – CO – O - R FOUR GROUPS WE WILL STUDY alcohol ester Carboxylic acid ether 1 oxygen Single bond 2 oxygens Double bond 1 R group 2 R groups

“Hydroxyl” refers to –OH “Carbonyl” refers to C=O “Carboxyl” refers to COOH Which functional groups contain –a hydroxyl group? Alcohols, carboxylic acids –a carbonyl group? aldehydes, ketones, carboxylic acids, amides, esters –a carboxyl group? carboxylic acids OTHER NAMES THAT DESCRIBE PATTERNS OF ATOMS THAT ARE PARTS OF FUNCTIONAL GROUPS. For more lessons, visit

14 Functional groups are very important because… Functional groups determine all of the following properties of a molecule:  Bonding and shape  Type and strength of intermolecular forces  Physical properties  Nomenclature  Chemical reactivity

15 Ethane : This molecule has only C — C and C — H bonds no polar bonds, no lone pairs, so it has no reactive sites ethane and molecules like it are very unreactive. Ethanol : has lone pairs and polar bonds that make it reactive with a variety of reagents. The OH group makes the properties of ethanol very different from the properties of ethane. EXAMPLE

17 Solubility is the extent to which a compound, called a solute, dissolves in a liquid, called a solvent. In dissolving a compound, the energy needed to break up the interactions between the molecules or ions of the solute comes from new interactions between the solute and the solvent. Solubility

18 Compounds dissolve in solvents having similar kinds of intermolecular forces. “Like dissolves like.” Polar compounds dissolve in polar solvents. Nonpolar or weakly polar compounds dissolve in nonpolar or weakly polar solvents. Water and organic solvents are two different kinds of solvents. Water is very polar and is capable of hydrogen bonding with a solute. Many organic solvents are either nonpolar, like carbon tetrachloride (CCl 4 ) and hexane [CH 3 (CH 2 ) 4 CH 3 ], or weakly polar, like diethyl ether (CH 3 CH 2 OCH 2 CH 3 ). Most ionic compounds are soluble in water, but insoluble in organic solvents.

19 An organic compound is water soluble only if it contains one polar functional group capable of hydrogen bonding with the solvent for every five C atoms it contains. For example, compare the solubility of butane and acetone in H 2 O and CCl 4.

20 Since butane and acetone are both organic compounds having a C—C and C—H backbone, they are soluble in the organic solvent CCl 4. Butane, which is nonpolar, is insoluble in H 2 O. Acetone is soluble in H 2 O because it contains only three C atoms and its O atom can hydrogen bond with an H atom of H 2 O.

21 To dissolve an ionic compound, the strong ion-ion interactions must be replaced by many weaker ion-dipole interactions. Figure 3.4 Dissolving an ionic compound in H 2 O

22 The size of an organic molecule with a polar functional group determines its water solubility. A low molecular weight alcohol like ethanol is water soluble since it has a small carbon skeleton of  five C atoms, compared to the size of its polar OH group. Cholesterol has 27 carbon atoms and only one OH group. Its carbon skeleton is too large for the OH group to solubilize by hydrogen bonding, so cholesterol is insoluble in water.

23 The nonpolar part of a molecule that is not attracted to H 2 O is said to be hydrophobic. The polar part of a molecule that can hydrogen bond to H 2 O is said to be hydrophilic. In cholesterol, for example, the hydroxy group is hydrophilic, whereas the carbon skeleton is hydrophobic.