Alcanos-nomeclatura, Propiedades Físicas

1. Alcanos

Hidrocarburos

Son compuestos formados exclusivamente por carbono e hidrgeno.

Alcanos

Los alcanos son hidrocarburos saturados, estn formados exclusivamente por carbono e hidrgeno y nicamente hay enlaces sencillos en su estructura.

Frmula general: CnH2n+2 donde n represente el nmero de carbonos del alcano.

Esta frmula nos permite calcular la frmula molecular de un alcano. Por ejemplo para el alcano de 5 carbonos: C5H [(2 x 5) +2] = C5H12

Hidrocarburos.

Molculas que contienen slo hidrgeno y carbono (CxHy)

Familias de hidrocarburos:

HIDROCARBUROS

ACCLICOS

CCLICOS

CARBOCCLICOS

ALIFTICOS (ALICCLICOS)

AROMTICOS

Hidrocarburos acclicos

Alcanos: CnH2n+2 (enlaces )

Alquenos: CnH2n (enlaces )

Alquinos: CnH2n-2 (enlaces )

Hidrocarburos alicclicos

Cicloalcanos

Cicloalquenos

Cicloalquinos

Alcanos

El estado fsico de los 4 primeros alcanos: metano, etano, propano y butano es gaseoso.

Del pentano al hexadecano (16 tomos de carbono) son lquidos y a partir de heptadecano (17 tomos de carbono) son slidos.

El punto de fusin, de ebullicin y la densidad aumentan conforme aumenta el nmero de tomos de carbono.

Son insolubles en agua

Propiedades de los Alcanos

Pueden emplearse como disolventes para sustancias poco polares como grasas, aceites y ceras.

El gas de uso domstico es una mezcla de alcanos, principalmente propano.

El gas de los encendedores es butano.

El principal uso de los alcanos es como combustibles debido a la gran cantidad de calor que se libera en esta reaccin.

Propiedades de los Alcanos

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Nomenclature:

The name of every organic molecule has 3 parts:

1. The parent name indicates the number of carbons in

the longest continuous chain.

2. The suffix indicates what functional group is present.

3. The prefix tells us the identity, location, and number of

substituents attached to the carbon chain.

Alkanes

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The carbon substituents bonded to a long carbon chain are called alkyl groups.

An alkyl group is formed by removing one H atom from an alkane.

To name an alkyl group, change the ane ending of the parent alkane to yl. Thus, methane (CH4) becomes methyl (CH3-) and ethane (CH3CH3) becomes ethyl

(CH3CH2-).

Alkanes

Nomenclature:

10

Naming three- or four-carbon alkyl groups is more

complicated because the substituent can have isomeric

forms. For example, propane has both 1 and 2 H atoms, and removal of each of these H atoms forms a

different alkyl group with a different name, propyl or

isopropyl.

Alkanes

Nomenclature:

11

1. Find the parent carbon chain and add the suffix.

The parent is the longest continuous chain of carbon atoms.

Alkanes

Rule 1:

12

Note that if there are two chains of equal length, pick the

chain with more substituents to simplify naming. In the

following example, two different chains in the same

alkane have seven C atoms. We circle the longest

continuous chain as shown in the diagram on the left,

since this results in the greater number of substituents.

Alkanes

Nomenclature:

13

2. Number the atoms in the carbon chain from the end

that gives the first substituent the lowest number.

Alkanes

Rule 2:

14

If the first substituent is the same distance from both

ends, number the chain to give the second substituent

the lower number.

Alkanes

Nomenclature:

15

When numbering a carbon chain results in the same

numbers from either end of the chain, assign the lower

number alphabetically to the first substituent.

Alkanes

Nomenclature:

16

3. Name and number the substituents.

Name the substituents as alkyl groups.

Every carbon is part of the longest chain or a part of a substituent, not both.

Each substituent needs its own number.

If two or more identical substituents are bonded to the longest chain, use prefixes to indicate how many: di- for

two groups, tri- for three groups, tetra- for four groups,

etc.

Alkanes Rule 3:

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4. Finally, write the name.

Substituent names and numbers come before the parent.

List substituents in alphabetical order, ignoring all prefixes except iso, as in isopropyl and isobutyl.

Separate numbers by commas and separate numbers from letters by hyphens. The name of an alkane is a

single word, with no spaces after hyphens and commas.

Alkanes

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Carbon atoms in alkanes and other organic compounds are classified by the number of other carbons directly

bonded to them.

Alkanes Introduction:

19

Hydrogen atoms are classified as primary (1), secondary (2), or tertiary (3) depending on the type of carbon atom to which they are bonded.

Alkanes

Introduction:

20

Degrees of Substitution Primary (1) Carbon: carbon that is bonded to only one other carbon Secondary (2) Carbon: carbon that is bonded to two other carbons Tertiary (3) Carbon: carbon that is bonded to three other carbons Quarternary (4) Carbon: carbon that is bonded to four other carbons

1 Hydrogens- hydrogens on a primary carbon. -CH3 (methyl group) 2 Hydrogens- hydrogens on a secondary carbon. -CH2- (methylene group) 3 Hydrogens- hydrogens on a tertiary carbon. CH (methine group)

HO

Primary (1) Secondary (2) Tertiary (3)Quarternary (4)

secondaryalcohol

H3C CH2 CH

CH3

CH2 C

CH3

CH3

CH3

methyl group: 1 hydrogens methylene group: 2 hydrogens methine group: 3 hydrogens

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The maximum number of possible constitutional isomers increases dramatically as the number of

carbon atoms in the alkane increases. For example,

there are 75 possible isomers for an alkane having 10

carbon atoms, but 366,319 possible isomers for one

having 20 carbons.

The suffix ane identifies a molecule as an alkane.

By increasing the number of carbons in an alkane by a CH2 group, one obtains a homologous series of alkanes, as shown in Table 4.1. The CH2 group is

called methylene.

Alkanes

Introduction:

1.- La base del nombre fundamental, es la cadena continua ms larga de tomos de carbono.

2.- La numeracin se inicia por el extremo ms cercano a una ramificacin.

Dos ramificaciones a la misma distancia, se empieza a numerar por el extremo ms cercano a la ramificacin de menor orden alfabtico.

Dos ramificaciones del mismo nombre a la misma distancia de cada uno de los extremos, se busca una tercera ramificacin y se numera la cadena por el extremo ms cercano a ella.

Nomenclatura de Alcanos

Hydrocarbons

CH4

C2H6

C3H8

C4H10

methane

ethane

propane

butane

C6H14

C7H16

C8H18

C9H20

C10H22

hexane

heptane

octane

nonane

decane

Prefix Suffix

meth-

eth-

prop-

but-

hex-

hept-

oct-

non-

dec-

-ane

-ane

-ane

-ane

-ane

-ane

-ane

-ane

-ane

Formula Name Structure

H

C

H

HH

H3C CH3

C5H12 pentanepent- -ane

Hydrocarbons

CH4

C2H6

C3H8

C4H10

methane

ethane

propane

butane

Prefix Suffix

meth-

eth-

prop-

but-

-ane

-ane

-ane

-ane


H3C C CH3

H

H

H3C C C CH3

HH

H H

H

C

H

HH

or

or

H

C

H

CH H

H

H

C4H10 but- -ane H3C C CH3

CH3

H

or

Hydrocarbons

iso-butane

Hydrocarbons

C4H10 butane

Prefix Suffix

but- -ane


H3C C C CH3

HH

H H

or

C4H10 iso-butanebut- -ane H3C C CH3

CH3

H

or

C5H12 pentanepent- -ane H3C C C C

HH

H H

H

H

CH3 or

H3C C C C

CH3H

H H

H

H

H

H C C C

CH3H

H CH3

H

H

H

or

or

C5H12 iso-pentanepent- -ane

C5H12 iso-pentane???pent- -ane

HydrocarbonsHydrocarbons

C4H10 butane

Prefix Suffix

but- -ane


H3C C C CH3

HH

H H

or


CH3

H

or


HH

H H

H

H

CH3 or

H3C C C C

CH3H

H H

H

H

H

H C C C

CH3H

H CH3

H

H

H

or

or

C5H12 iso-pentanepent- -ane

C5H12 neo-pentanepent- -ane

HydrocarbonsHydrocarbons

3.- Cuando en un compuestos hay dos o ms ramificaciones iguales:

4.- Se escriben las ramificaciones en orden alfabtico y el nombre del alcano que corresponda a la cadena principal.



Radicales alquilo Cuando alguno de los alcanos pierde un tomo de hidrgeno se forma un

radical alquilo. Estos radicales aparecen como ramificaciones sustituyendo tomos de hidrgeno en las cadenas.

IUPAC System of Naming Organic Compounds

pentaneH3C C C C

HH

H H

H

H

CH3

H3C C C C

CH3H

H H

H

H

H

H C C C

CH3H

H CH3

H

H

H

2-methylbutane

2,2-dimethylpropane

1. Find the longest carbon chain

2. Name all the atoms (other than H) not in the longest chain as groups

3. Number groups from the end of the chain closest to the first group

4. List multiple groups in alphabetical order,

1

2

3

4

5

Longest chain: pentane

Groups: none

IUPAC Name

12

34 Longest chain: butane

Groups: one methyl

12

34

not:

not: 3-methylbutane

12

3Longest chain: propane

Groups: two methyls

C4H10 butane

Prefix Suffix

but- -ane

Formula Structure

H3C C C CH3

HH

H H

or


CH3

H


HH

H H

H

H

CH3

H3C C C C

CH3H

H H

H

H

H

H C C C

CH3H

H CH3

H

H

H

C5H12 pent- -ane

C5H12 pent- -ane

Hydrocarbons

IUPAC Name

2-methyl butane

2,2-dimethylpropane

IUPAC System of Naming Organic Compounds

CH3

C2H5

C4H9

methyl

ethyl

butyl

Prefix Suffix

meth-

eth-

but-

-yl

Group Formula Name Structure

C C C CH3

HH

H H

H

C

H

H

or

H

C

H

C H

H

H

-yl

-yl

H

H

C3H7 propylprop-C C CH3

H

H

or-yl

H

H

C3H7 iso-propyliso-prop-H3C C CH3

H

or-yl

Abbreviation

Me

Et

Pr

Bu

iPr

Naming Branches as Groups


C4H9

sec-butyl


C4H9

iso-butyl

C4H9 tert-butyl

Other Groups We May Encounter

C5H11 neo-pentyl

F

Cl

Br

I

bromo

fluoro

chloro

iodo

F

Cl

Br

I



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Rules for Systematic Nomenclature of Alkanes

1. Find the parent chain

a. Identify the longest continuous carbon chain as the

parent chain.

b. If more than one different chains are of equal length

(number of carbons), choose the one with the greater

number of branch points (substituents) as the parent.

CH3 CHHC

CH2

CH2

CH2 CH2

CH3

CH3

CH3

7 carbons = hept-

CH3 CHHC

CH3

CH2

CH2 CH3

CH2 CH3 CH3 CH CH

CH3

CH2

CH2 CH3

CH2 CH3

2 branch pts. 1 branch pt.

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2. Numbering the carbons of the parent chain

a. Number the carbon atoms of the parent chain so that any

branch points have the lowest possible number

b. If there is branching equidistant from both ends of the

parent chain, number so the second branch point has the

lowest number.

CH3 CHHC

CH2

CH2

CH2 CH2

CH3

CH3

CH3

CH3 CHHC

CH2

CH2

CH2 CH2

CH3

CH3

CH3

1

2

3

7 123

45

5

4

6

6

7

branch pts. at carbons 3 and 4 branch pts. at carbons 4 and 5

4

CH3 CH CH2

CH2

CH2 CH CH

CH3

CH2 CH3

1 2

3 5 6 7 8 9

H3C CH2 CH3

6

CH3 CH CH2

CH2

CH2 CH CH

CH3

CH2 CH3

9 8

7 5 4 3 2 1

H3C CH2 CH3

branch pts. at carbons 3, 6, 7 branch pts. at carbons 3,4,7

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3. Substituents

a. Identify and number the substituents and list

them in alphabetical order.

b. If there are two substituents on the same carbon,

assign them the same number.

4. Write out the name

a. Write out the name as a single word:

hyphens (-) separate prefixes

commas (,) separate numbers

b. Substituents are listed in alphabetical order c. If two or more identical substituents are present use the

prefixes: di- for two

tri- for three

tetra- for four

6

CH3 CH CH2

CH2

CH2 CH CH

CH3

CH2 CH3

9 8

7 5 4 3 2 1

H3C CH2 CH3Parent C-9 = nonane3- ethyl4-methyl7-methyl

4,7-dimethyl

37

note: these prefixes (di-, tri-, tetra-, etc.) are not used for

alphabetizing purposes

6

CH3 CH CH2

CH2

CH2 CH CH

CH3

CH2 CH3

9 8

7 5 4 3 2 1

H3C CH2 CH3

3- ethyl-4,7-dimethylnonane

5. Complex Substituents (substituents with branching)

a. Named by applying the four previous rules with some

modification

b. Number the complex substituent separately from the parent.

Begin numbering at the point of attachment to the parent

chain

c. Complex substituents are set off by parenthesis.

CH3 CH CH2

CH3

CH2 CH CH CH2 CH2 CH2

H2C CH2

CH3

CH3

CH3

1 2 3 4 5 6 7 8 9 10

1 2 3 2,6-dimethyl-5-(1-methylpropyl)decane

CH2

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Nonsystematic (trivial) Names:

3-carbons:

4-Carbons:

5- Carbons:

Alphabetizing trivial names:

Iso- and neo are part of the alkyl group name and are used for alphabetizing.

sec- and tert- are not included in the alphabetical order.

4-(1-methylethyl)heptane-or-

4-Isopropylheptane

2-methyl-6-(2-methylpropyl)decane-or-

6-Isobutyl-2-methyldecane

CH

H3C

H3C

Isopropyl-

(1-methylethyl)

Parent Chain

CH

CH2

H3C

Parent Chain

sec-butyl-

(1-methylpropyl)

Isobutyl-

(2-methylpropyl)

C

CH3

CH3

tert-butyl-

(1,1-dimethylethyl)

H3C

CH2Parent Chain

CH3

CHH3C H3CParent Chain

C

CH3

CH3

tert-pentyl-, tert-amyl

(1,1-dimethylpropyl)

CH2Parent ChainH3CCH2C

Parent ChainH3C

CH3

CH3

neopentyl-

(2,2-d imethylpropyl)

Isopentyl-, isoamyl

(3-methylbutyl)

CH2Parent Chain

CH2CH

H3C

H3C

Ejemplos de Alcanos

4-ETIL-2-METILHEPTANO

Ejemplos de Alcanos

5-ISOPROPIL-3- METILNONANO

3-METIL-5-n-PROPILOCTANO

EJEMPLOS DE ALCANOS

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Alkanes

Physical Properties of Alkanes:

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Alkanes

Physical Properties of Alkanes:

Documents

Alcanos-nomeclatura, Propiedades Físicas