Organic molecules improve the quality of everyone’s life.

Organic Chemistry = The chemistry of C and its compounds. Including those that contain N, O, S, P and

halogens.Organic molecules constitute the chemical building blocks of life:

Fats SugarsProteins Amino acids

Organic molecules are part of everyday life:Clothes Toothbrush SoapShampoo Deodorant

FurnitureCarpet Paint Food

Organic molecules give rise to large industrial processes:Petroleum refiningPlasticsPharmaceuticals

propofol isoflurane

Drugs given to induce or maintain general anesthesia are either given as: Gases or vapors (inhalational anesthetics) Injections (intravenous anesthetics)

Most commonly, these two forms are combined, with an injection given to induce anesthesia and a gas used to maintain it, although it is possible to deliver anesthesia solely by inhalation or injection.

Hydrocarbons = compounds of C and H

4 single bonds saturatedDouble or triple unsaturated

11.2 Alkanes

IUPAC (pronounced “I-YOU-PACK”)

4 single bonds saturated alkanes

Condensed Structures

•Some bond lines can be drawn in for effect or to show specific bonding.

•Identical groups can be condensed further:

Cycloalkanes

Compounds can be:

• Straight-chain alkane: An alkane that has all its carbons connected in a row.

• Cyclic: carbon atoms connect in a cyclic structure.

• Branched-chain alkane: An alkane that has a branching connection of carbons.

Straight and branched compounds can be related as:

Constitutional isomers: Compounds with the same molecular formula but different connections among their atoms.

Petroleumo An important source of alkanes, mostly linear, but some

branched and aromatics.o Breaking an alkane down into smaller fractions is known as

cracking.o Cracking takes place in the oil-refining industry where

gasoline and other fuels are obtained from petroleum.

When the substituent is a C structure it is called a branch.• Branches are named as alkyls.

• Alkyls are alkanes whose structures are missing a H.

11.3 Alkanes with Substituents

Early 19th century (1800-1830)Compounds were often named at the whim of their discoverers:

Formic acid isolated from antsnamed after the Latin word for ant, formica.

Urea isolated from urine

morphine painkiller named after the Greek God of dreams, Morpheus.

Barbituric acid Adolf von Baeyer named this compound in honor of a woman named Barbara.

End of 19th century (1892) 34 European chemists met in Switzerland and developed a system of organic nomenclature. IUPAC (pronounced “I-YOU-PACK”) Systematic names

Common names

In the IUPAC system for organic compounds, a chemical name has three parts: prefix, parent, and suffix.

Write the name as a single word, using hyphens to separate the numbers from the different prefixes and commas to separate numbers if necessary. If two or more different substituent groups are present, cite them in alphabetical order.

If there are two substituents on the same carbon, assign the same number to both. There must always be as many numbers in the name as there are substituents.

3-ethyl-3-methylhexane

Modifiers di-, tri-…. Are not used in alphabetical ordering

sec-, tert-… ignoredCommon names

iso-, neo-… considered

If two or more substituents are the same use modifiers di-, tri-, tetra-, …….

Example

Select the parent chain

Number the chain so as to give the subs their lowest possible value.

Write in alphabetical order

One substituentNo need to number the C chainThe name of a substituent is placed in front of the cycloalkane name.

Naming cycloalkanes

Two substituentsYes need to number the C chainposition #1 to 1st in alphabet, then move in a direction that gives the lower number to the 2nd sub.

CH3

F

CH2CH3

methylcyclobutane

1-ethyl-2-fluorocyclopentane1-ethyl-3-methylcyclohexane

Three or more substituents• Goal = get lowest possible numbering sequence.• Begin @ sub that leads to the lowest set of locants.• If 2 possible sequences, alphabetical order takes precedence.

Cl Cl

1

231 2

3

1-chloro-3-ethyl-2-methylcyclopentane

CH3CH3CH2

Br

CH3CH3CH2

Br

1

3 5

1

35

1-bromo-3-ethyl-5-methylcyclohexane

If a conflict exists, lowest locants override alphabet.

CH3

CH2CH3

Cl

CH3

CH2CH3

Cl

4-chloro-2-ethyl-1-methylcyclohexane

Gives the lowest set of locants1

4

31

2

4

Always search for the lowest set of locants.

1,1,3-trimethylcyclohexane Not 1,3,3,…..

12

3 12

3

11.4 Properties of Alkanes• Odorless or mild odor; colorless; tasteless; nontoxic• Nonpolar; insoluble in water but soluble in nonpolar organic solvents; less dense than water• Flammable; otherwise not very reactive• The first four alkanes are gases at room temperature and pressure, alkanes with 5–15 carbon atoms

are liquids; those with 16 or more carbon atoms are generally low-melting, waxy solids.

Alkanes- Least reactive class of organic compounds- their inertness allows them to act as solvents, mediums for other reactions to take

place.- they still undergo 2 main reactions- Combustion – most important source of heat energy- Halogenation – adds a halogen (X = F, Cl, Br, I) bringing added reactivity

Reactions of Alkanes

Combustion- Stoichiometry of the reactants is important

- If sufficient O2 is supplied- CH3CH2CH3 + 5 O2 3 CO2 + 4 H2O + heat

- If insufficient O2 is supplied- CH3CH2CH3 + 4 O2 CO2 + 2 CO +4 H2O +

heat

Cycloalkane CH2 Units ΔH 25º ΔH 25º Ring Strain (CH2)n n kcal/mole per CH2 Unit kcal/mole

Cyclopropane n = 3 468.7 156.2 27.6Cyclobutane n = 4 614.3 153.6 26.4Cyclopentane n = 5 741.5 148.3 6.5Cyclohexane n = 6 882.1 147.0 0.0Cycloheptane n = 7 1035.4 147.9 6.3Cyclooctane n = 8 1186.0 148.2 9.6Cyclononane n = 9 1335.0 148.3 11.7Cyclodecane n = 10 1481 148.1 11.0CH3(CH2)mCH3 m = large — 147.0 0.0

Heat of combustion

The main source of ring strain in smaller rings is angle strain and eclipsing strain. Cyclopropane and cyclobutane have large contributions of both strains, with angle strain being especially severe.

- Heat of combustion data provide a measure of stability-Degree of stability is accounted for by subtle structural variations. -In small-ring cyclic compounds, ring strain can be a major contributor to stability and consequently reactivity.

Although the line drawings of simple cycloalkanes are geometrical polygons, the actual shape of these compounds in most cases is very different.

Cyclopropane is necessarily planar (flat), with the carbon atoms at the corners of an equilateral triangle. The 60º bond angles are much smaller than the optimum 109.5º angles of a normal tetrahedral carbon atom, and the resulting angle strain influences its chemical behavior. Cyclopropane also suffers substantial eclipsing strain, since all the carbon-carbon bonds are fully eclipsed.

Cyclobutane reduces some bond-eclipsing strain by folding (the out-of-plane dihedral angle is about 25º), but the total eclipsing and angle strain remains high.

Cyclopentane has very little angle strain (the angles of a pentagon are 108º), but its eclipsing strain would be large (about 10 kcal/mol) if it remained planar. Consequently, the five-membered ring adopts non-planar puckered conformations whenever possible.

Some Conformations of Cyclohexane Rings

A planar structure for cyclohexane is clearly improbable. The bond angles would necessarily be 120º, 10.5º larger than the ideal tetrahedral angle. Also, every carbon-carbon bond in such a structure would be eclipsed. The resulting angle and eclipsing strains would severely destabilize this structure. If two carbon atoms on opposite sides of the six-membered ring are lifted out of the plane of the ring, much of the angle strain can be eliminated. This boat structure still has two eclipsed bonds (colored magenta in the drawing) and severe steric crowding of two hydrogen atoms on the "bow" and "stern" of the boat. This steric crowding is often called steric hindrance. By twisting the boat conformation, the steric hindrance can be partially relieved, but the twist-boat conformer still retains some of the strains that characterize the boat conformer. Finally, by lifting one carbon above the ring plane and the other below the plane, a relatively strain-free chair conformer is formed. This is the predominant structure adopted by molecules of cyclohexane.

• A characteristic feature of organic molecules that behave in a predictable way. • Composed of an atom or group of atoms. • Groups that replace a H in the corresponding alkane.• A way to classify families of organic compounds.

11.5 Functional Groups

•The letter R is used to abbreviate the carbon and hydrogen portion of a molecule.

2. Convert each compound into its condensed and line-bond structural formulas?

3. Give the IUPAC name for each of the following:

1. All of the following are formulas of organic compounds except: a. C4H10 b. CH3CH2OH c. KCl d. CH3CH2Cl e. NH4Cl

Extra Credit (+15 HW points not to exceed 100) Due right at the end of the chapter

4. Compounds comprised of the same number and kinds of atoms but different in their atomic arrangement are known as:

a. Isotopes b. Isomers c. Homologs d. allotropes

5. How many compounds having the formula C3H8 are possible?

a. one b. two c. three d. four

6. How many compounds having the formula C6H14 are possible?

a. four b. five c. six d. seven

7. Provide the name:

8. Provide the name:

a. alkane, ether, alcohol, aldehyde

b. aromatic, ether, ester, ketone

c. alkene, ester, aromatic, alcohol

d. aromatic, ether, alkene, ester

10. Classify the following organic compounds according to their functional groups:

9. Sunscreens contain compounds that absorb UV light, such as 2-ethylhexyl p-methoxycinnamate. The functional groups in this compound are: