ORGANIC CHEMISTRY-ppt03

8/7/2019 ORGANIC CHEMISTRY-ppt03

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What is Organic Chemistry ?

The study of the compounds of carbon.

Some carbon compounds arenot consideredto be

organic, suchas CO2, CO, salts of carbon-

containing polyatomic ions (e.g., CO32-, CN-).

Inorganic chemistry is the study of the other

elements andnon-carbon containing compounds


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Carbon

Carbon is unique since it can form single, double, & triple

bonds with itself and with other atoms

Carbonatoms can form stable bonds to many other

elements (H, F, Cl, Br, I, O, N, S, P, etc.). Most organiccompounds containa few hydrogens, and sometimes

oxygen, nitrogen, sulfur, phosphorus, etc.

Carbonatoms can form complex structures, suchas long

chains, branched chains, rings, chiral compounds, etc.

Because of this variety in bonding and complexity, carbon

atoms can formatremendous variety of compounds.


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Hydrocarbon: Alkane

A hydrocarbon is a compoundconsisting of only hydrogen (H)andcarbon (C).

The carbonto carbon can be single,double , or triple bonds.

AlkanesAlkanes arehydrocarbons with onlysingle bonds.single bonds.

Alkane: saturatedhydrocarbons

(CnH2n+2) Saturated: only single bonds

They arealso calledaliphaticcompounds


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Structure

Saturatedhydrocarbons can be:

linear (general formula CnH2n + 2)

branched (general formula CnH2n + 2, n > 3)

cyclic (general formula CnH2n, n > 2).

The former two arealkanes, whereas thethird group is called cycloalkanes.

Shape

tetrahedralabout carbon

all bondangles areapproximately 109.5

The simplestpossiblealkane (theparentmolecule) is Methane (CH4).


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Drawing Alkanes

Whena structure is drawnto show eachbond, it is calledacomplete structuralformula (expanded structural formula).

Incondensed structural formulas, only

specific bonds are shown;this is useful inreducing the number of CH bonds thatmust bedrawn

Inline drawings (line-angle formulas),bonds are represented by lines;

everywheretwo lines meet or alinebegins or ends is a C atom. Hs on Cs arenot shown (except for emphasis). Hs onother atoms must be shown


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Example: Drawing Alkane

Draw acceptable condensed structures andline drawingsassociated withthe following expanded structural formulas


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Alkane Nomenclature

IUPACIUPAC (International Union of Pure and Applied Chemistry)(International Union of Pure and Applied Chemistry) Rules forRules forAlkaneAlkane NomenclatureNomenclature Findandnamethelongest continuous carbon chain. This is calledtheFindandnamethelongest continuous carbon chain. This is calledtheparentparent

chainchain. (Examples: methane, propane, etc.). (Examples: methane, propane, etc.)

Number the chain consecutively, starting attheendnearestanattached groupNumber the chain consecutively, starting attheendnearestanattached group

((substituentsubstituent).). Identify andname groups attachedto this chain. (Examples: methylIdentify andname groups attachedto this chain. (Examples: methyl--,, bromobromo--,,

etc.)etc.)

Designatethelocation of each substituent group withthenumber of the carbonDesignatethelocation of each substituent group withthenumber of the carbonparent chain on whichthe group is attached.parent chain on whichthe group is attached. PlaceadashPlaceadashbetweennumbersbetweennumbersandletters. (Example: 3andletters. (Example: 3--chloropentane)chloropentane)

Assemblethename, listing groups inalphabetical order.Assemblethename, listing groups inalphabetical order.

TheprefixesTheprefixes didi, tri, tetraetc., usedto designate several groups of the, tri, tetraetc., usedto designate several groups of thesamekind, arenot considered whenalphabetizing.samekind, arenot considered whenalphabetizing. Placea commaPlacea commabetweenmultiplenumbers. (Example: 2,3betweenmultiplenumbers. (Example: 2,3--dichloropropane)dichloropropane)


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Step 1: Findtheparent chain.Findtheparent chain.

Where is theWhere is thelongest continuous chain oflongest continuous chain of

carbonscarbons ??

SubstituentsSubstituents - ParentParent

The Parent tells us how many carbon atomscan be found in the longest chain.The substituents indicate any groups that are

attached to the longest carbon chain.


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Prefixes for # of CarbonsPrefixes for # of Carbons

11 MethMeth 66 HexHex

22 EthEth 77 HeptHept

33 PropProp 88 OctOct

44 ButBut 99 NonNon

55 PentPent 1010 DecDec


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EndingEnding

AlkAlkaneaness (all C(all C--C single bondedparent chain)end inC single bondedparent chain)end inaneane

MethMethaneane CHCH44

EthEthaneane CC22HH66 PropPropaneane CC33HH88

Attached carbon groups (Attached carbon groups (substituentssubstituents)end in)end inylyl

MethMethylyl CHCH33 --

EthEthylyl CHCH33CHCH22--

PropPropylyl CHCH33CHCH22CHCH22


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Step 2: Number theparent chain.Number theparent chain.

Number theparent chain so thattheattached

groups are onthelowestnumbers (

5 4 3 2 1

1 2 3 4 5

Methyl is on carbon #2 of theparent chain

Methyl is on carbon #4 of theparent chain

GREEN is the rightGREEN is the rightway for this one!way for this one!


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Step 3: Nametheattached groups.Nametheattached groups.

Carbon (alkCarbon (alkylyl) groups) groups

MethMethylyl CHCH33 --

EthEthylyl CHCH33CHCH22--

PropPropylyl CHCH33CHCH22CHCH22 HalogensHalogens

FluoroFluoro (F(F--))

ChloroChloro ((ClCl--))

BromoBromo (Br(Br--))

IodoIodo (I(I--))


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Step 4: Designate wherethe group isDesignate wherethe group is

attachedto theparent chain.attachedto theparent chain.

Usethenumbers of theparent chain from step 2 to

designatethelocation of theattached groups to the

parent chain.

1 2 3 4 5


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Step5: Alphabetizethe groups,Alphabetizethe groups,

combinelike groups, andassemble.combinelike groups, andassemble.

Useanumericalprefix to indicate whenmorethan one of a same substituentexists inthemolecule)

Prefixes arenot considered whenalphabetizingarenot considered whenalphabetizing(Example: dimethyl =m for alphabetizing)

Parent chain goeschain goes LAST: The substituents arelistedalphabetically before theparent

Comma: numeral,numeralComma: numeral,numeral

Dash: numeralDash: numeral--letter orletter or

letterletter--numeralnumeral


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Numerical Prefixes for NamingNumerical Prefixes for Naming

Identical GroupsIdentical Groups


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Example: IUPAC Nomenclature

Provideacceptable IUPAC names for the following molecules


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Givethenames of the following compounds using IUPACnomenclature


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Draw Some Simple Alkanes:

22--methylpentanemethylpentane

33--ethylhexaneethylhexane

2,32,3--dimethylbutanedimethylbutane

Draw condensed structural formulas or linedrawings for each of the following compounds

3-ethylpentane

2,2-dimethylbutane

3-ethyl-2-methylhexane


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Common Name

Thenumber of carbons inthealkane determines thename allalkanes with four carbons are butanes, those with five

carbons arepentanes, etc.

iso- indicates the chainterminates in-CH(CH3)2 , neo- that itterminates in-C(CH3)3

CH3 CH2 CH2 CH2 CH3

CH 3 CHCH3

CH 3

CH3 CH2 CHCH3

CH3

CH3CH

2CH 2CH 3

CH3CCH3

CH3

CH3

Pe n tan e Is op e n tan e

I s o buta neButane

N e o p e n t a n e


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Classification of C & H

Primary (1Primary (1) C:) C: a carbon bondedto one other carbon 1 H: ahydrogen bondedto a 1 carbon

Secondary (2Secondary (2) C:) C: a carbon bondedto two other carbons 2 H: ahydrogen bondedto a 2 carbon

Tertiary (3Tertiary (3) C:) C: a carbon bondedto three other carbons 3 H: ahydrogen bondedto a 3 carbon

Quaternary (4Quaternary (4) C) C: a carbon bondedto four other carbons


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Example:

Designateeach carbon of these compounds as

primary, secondary, tertiary, or quaternary:


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Physical Properties of Alkanes

Nonpolar

Insoluble in water.

Lower density than water.

Low boiling andmelting points. Gases with 1-4 carbonatoms

methane, propane, butane

Liquids with5-17 carbonatoms

kerosene, diesel, and jet fuels:

Solids with 18 or more carbonatoms

wax, paraffin, Vaseline


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Chemical reactions of Alkanes

Combustion:Combustion:

Alkanes react with oxygen.

CO2, H2O, andenergy areproduced.

Alkane + O2 CO2 + H2O +

heat

CH4 + 2O2 CO2 + 2H2O +

energy


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Halogenation:

Alkanes react with Halogens.

CH4 + Cl2 CH3Cl + CH2Cl2 CHCl3 CCl4+ +

heat or light

=>


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Properties Of Alkane

Alkane Formula

Boiling point

[C]

Melting point

[C]

Density [gcm3]

(at 20C)

Methane CH4 -162 -183 gas

Ethane C2H6 -89 -182 gas

Propane C3H8 -42 -188 gas

Butane C4H10 0 -138 gas

Pentane C5H12 36 -130 0.626(liquid)

Hexane C6H14 69 -95 0.659(liquid)

Heptane C7H16 98 -91 0.684(liquid)

Octane C8H18 126 -57 0.703(liquid)

Nonane C9H20 151 -54 0.718(liquid)

Decane C10H22 174 -30 0.730(liquid)

Undecane C11H24 196 -26 0.740(liquid)

Dodecane C12H26 216 -10 0.749(liquid)

Icosane C20H42 343 37 solid

Triacontane C30H62 450 66 solid

Tetracontane C40H82 525 82 solid


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Source of Alkanes

Natural gas 90 to 95percentmethane

5to 10 percentethane, and

amixture of other low-boiling alkanes, chiefly propane, butane,

and 2-methylpropane. Petroleum

A thickliquidmixture of thousands of compounds, most of themhydrocarbons formed fromthedecomposition of marineplants andanimals.


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Cycloalkanes

General formulaCCnnHH2n2n five- and six-membered rings arethemost common

Structureandnomenclature

to name, prefix thename of the corresponding open-chainalkane withcyclocyclo--,, andnameeach substituent onthe ring

if only one substituent, no needto give itanumber

if two substituents, number fromthe substituent of loweralphabetical order

if three or more substituents, number to givethemthelowestset of numbers andthenlist substituents inalphabeticalorder


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THANK YOU....THANK YOU....


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HOME WORKHOME WORK


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1

Provide IUPAC names for thesealkanes:


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2

Draw condensed structural formulas or line

drawings for each of the following compounds:

3-ethylpentane

2,2-dimethylbutane

3-ethyl-2-methylhexane

4-isopropyloctane

6-sec-butyl-7-ethyl-2,2,5,8-tetramethylnonane


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3

The following names have beenassigned incorrectly.

Draw the structure corresponding to thename, and

assignthe correct IUPAC name.

3-sec-butylpentane

2-ethyl-2,6-dimethylhexane

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ORGANIC CHEMISTRY-ppt03