4.5: Naphthenes nomenclature (2023)

introduce

Many organic compounds found in nature or created in the laboratory contain rings of carbon atoms with unique chemical properties. These compounds are called cycloalkanes. Cycloalkanes contain only carbon-hydrogen bonds and carbon-carbon single bonds, but in cycloalkanes, the carbon atoms are connected to form rings. The smallest cycloalkane is cyclopropane.

If you count the carbons and hydrogens, you will find that they no longer correspond to the general formula \(C_nH_{2n+2}\). Two hydrogen atoms are lost when carbon atoms are added to the ring. The general formula of the cycloalkane is \(C_nH_{2n}\). Cyclic compounds are not all planar molecules. All naphthenes from cyclopentane exist as "folded rings". For example, the ring structure of cyclohexane is shown below:

Figure 2: Shape-wise, this is known as the "chair" form of cyclohexane, which vaguely resembles a chair. Note: The cyclohexane molecule is constantly changing, the atoms on the left are currently pointing down and are flipped up, and the atoms on the right are flipped down. This creates a different (slightly less stable) form of cyclohexane, the so-called "boat" form. In this arrangement, the two atoms point up or down at the same time.

In addition to saturated cyclic hydrocarbons, cycloalkanes can also be multiple orfunctionalgroupFurther determine its unique chemical properties. The most common and useful cycloalkanes in organic chemistry are cyclopentane and cyclohexane, although others with different numbers of carbon atoms can be synthesized. Understanding naphthenes and their properties is crucial because many biological processes that occur in most organisms share naphthenic structures.

Glucose(6 carbon sugar)	ribosa(5 carbon sugar)	cholesterol(polycyclic)

Despite their importance, polycyclic compounds are complex and often have IUPAC-accepted common names. However, common names often do not conform to the basic IUPAC naming rules. The general formula of the cycloalkane is \(C_nH_{2n}\), where \(n\) is the number of carbon atoms. The naming of cycloalkanes follows a simple set of rules that is based on the same basic steps as the naming of alkanes. Cyclic hydrocarbons have the prefix "cyclo-".

Content

For convenience, a cycloalkane molecule can be represented in terms of a structural structure, assuming that each intersection between two lines has a carbon atom and the corresponding number of hydrogen atoms.

is the same as is the same as

naphthenic	molecular formula	basic structure
cyclopropane	C3h6
cyclobutane	C4h8
cyclopentane	C5h10
ciclohexano	C6h12
cycloheptan	C7h14
cyclooctane	C8hsixteen
cyclone	C9h18
ciclodecano	C10h20

IUPAC naming convention

1. Determine the naphthenes used as parent chains. The main chain is the chain with the most carbon atoms. When there are two naphthenes, use the naphthene with the higher carbon number as the backbone.
2. When linear alkyl chains with more carbon atoms than the cycloalkane are present, the alkyl chain should be used as the primary backbone. Cycloalkanes as substituents on alkyl chains have the suffix "-yl" and should therefore be referred to as cycloalkyl.

3) Determine whichfunctional groupor other rent groups.

4) Number the carbon atoms of cycloalkanes to minimize the number of carbon atoms with functional groups or alkyl groups. The number of carbons with multiple substituents must be less than the number of carbons with only one substituent or functional group. One way to get the lowest number possible is to number the carbon atoms so that their sum when adding the numbers corresponding to the substituents is as small as possible.

(1+3=4）NO (1+5=6）

5) When naming cycloalkanes, the substituents and functional groups should be listed in alphabetical order.

(Example: 2-Secondromo-1-CChlor-3-reyesethylcyclopentane)

6) Indicate the carbon number of the functional group with the highest priority in alphabetical order. There must be a hyphen “-” between the number and the name of the substituent. The name of the substituent can follow the carbon number and the hyphen. If there is only one substituent in the original chain, it is not necessary to specify the number of carbon atoms in the substituent.

(Example: 1-chlorocyclohexane or chlorocyclohexane are acceptable)

7) If there is more than one identical functional group on a carbon, write the number of carbons in twos, threes, or four times, depending on how many identical functional groups are present on that carbon. The numbers must be separated by commas, followed by the names of the function groups, which must be separated by hyphens. If there are two identical function groups, the name must be preceded by "di". If there are three identical function groups, the name must be preceded by "tri". If there are four identical functional groups, the name must be prefixed with "Tetra". However, these prefixes cannot be used to determine alphabetical sorting.

There should always be commas between numbers and hyphens between numbers and names.

Note that the "f" for fluorine comes before the "m" for methyl in alphabetical order. Although "di" comes before "f" alphabetically, it is not used to determine alphabetical order.

8) When the substituents of the cycloalkanes are related in the cis or trans configuration, add "cis-" or "trans-" before the structure name to indicate the configuration.

azul= carbonGelb= hydrogenVerde= chlorine

Note that both chlorine and methyl point in the same direction on the molecular axis and are therefore cis.

cis-1-chloro-2-methylcyclopentane

9) After naming all the functional groups and substituents and the corresponding numbers, follow the name of the cycloalkane, if applicable.

reactivity

The reactivity of cycloalkanes is very similar to that of alkanes, with the exception of very small cycloalkanes, particularly cyclopropane. Due to the bond angles in the ring, cyclopropane is significantly more reactive than expected. When carbon forms four single bonds, the bond angle is usually about 109.5°. In cyclopropane the bond angle is 60°.

Because the electron pairs are so close together, there is significant repulsion between the bond pairs connecting the carbon atoms, making the bonds easier to break.

Alcohol substituents in cycloalkanes.

In IUPAC nomenclature, alcoholic substituents (-OH) have the highest priority for carbon numbering. Carbon atoms with alcohol substituents should be marked with 1. Molecules containing alcohol groups end in "-ol", which indicates the presence of an alcohol group. When two alcohol groups are present, the molecule is prefixed with "di-" before "-ol" (diol). When three alcohol groups are present, the molecule is prefixed with " di-". prefix Prefix "tri"-" prefix before "-ol" (triplet), etc.

Other substituents of cycloalkanes

and many othersfunctional groupLike alcohols, which are discussed later in the organic chemistry course, they determine the final names of the molecules. The nomenclature of these functional groups is detailed below along with an explanation of their chemical properties.

Alkynes as substituents on cycloalkanes are not possible, although alkynes determine the suffix of the molecule name, since alkynes are planar and require the carbons in the ring to form 5 bonds, making the carbon atoms charged negative.

However, cycloalkanes with substituents containing triple bonds are also possible, if the triple bond is not directly attached to the ring.

resume

1. Identify the main chain: The main chain contains the largest number of carbon atoms.
2. Number the substituents in the chain so that the sum of the numbers is as small as possible.
3. Name the substituents and put them in alphabetical order.
4. If the stereochemistry of a compound is given, indicate the direction as part of the nomenclature.
5. Cyclic hydrocarbons have the prefix "cyclo-" and the suffix "-alkane" unless an alcohol substituent is present. When an alcohol substituent is present, the molecule has a "-ol" end.

glossary

• Alcohol: oxygen and hydrogen OH hydroxyl attached to a substituted alkyl group.
• I rent:The structure that forms when a hydrogen atom is removed from an alkane.
• Cycle:Compounds arranged in rings or closed chains.
• naphthenic:Saturated cyclic hydrocarbons, the general formula is CnH(2n). Cycloalkanes are alkanes in which the carbon atoms are linked to form a closed ring.
• Functional group:The atom or group of atoms that replaces a hydrogen atom in an organic compound, giving the compound its unique chemical properties and determining its reactivity.
• hydrocarbon:Compound containing only carbon and hydrogen atoms.
• Crowded: All the atoms that make up a compound are linked to other atoms by single bonds and there are no double or triple bonds.
• bone structure:A simplified structure that assumes that each intersection between two lines contains one carbon atom and the corresponding number of hydrogen atoms.

Ask

Name the following structures.(Note: These structures are complex for practical reasons and may not occur in nature.)

1）2）3)4）5）6）

7）

Draw the following structures.

8) 1,1-Dibrom-5-fluor-3-butil-7-metilciclooctano 9) Trans-1-Brom-2-clorociclopentano

10) 1,1-Dibrom-2,3-dicloro-4-propilciclobutan11) 2-Metil-1-etil-1,3-dipropilciclopentan12) Cicloheptan-1,3,5-triol

Name the following structures.

azul= carbonGelb= hydrogenPutrefaction= oxygenVerde= chlorine

13)14）15)sixteen)17）

18）19）

Answers to practice questions.

1) Cyclodecane 2) Chlorocyclopentane or 1-chlorocyclopentane 3) trans-1-chloro-2-methylcycloheptane

4) 3-Cyclopropyl-6-methyldecane 5) Cyclopentylcyclodecane or 1-Cyclopentylcyclodecane 6) 1,3-Dibrom-1-chlor-2-fluorocycloheptane

7) 1-ciclobutil-4-isopropilciclohexano

8）9）10）11）12）

13) Cyclohexane 14) Cyclohexanol 15) Chlorcyclohexane 16) Cyclopentylcyclohexane 17) 1-chloro-3-methylcyclobutane

18) 2,3-dimethylcyclohexanol 19) cis-1-propyl-2-methylcyclopentano

internal link

• alcohol nomenclature
• ether nomenclature
• Ester-Nomenklatur
• Alkene nomenclature
• Ketones and aldehydes nomenclature.
• alkyne nomenclature

external link

• More practice questions on naming naphthenes
• Wolfart, Costa. Organic chemistry. fifth edition.
• Wikipedia: cycloalkane
• http://www.cem.msu.edu/~reusch/VirtualText/nomen1.htm
• http://www.chemguide.co.uk/organicprops/alkanes/background.html
• http://www.cem.msu.edu/~reusch/VirtualText/nomen1.htm
• http://science.csustan.edu/nhuy/chem...IVNamecyal.htm
• http://en.wikibooks.org/wiki/Organic...s/Cycloalkanes

Reference

1. ACD/ChemSketch Freeware, version 11.0, Advanced Chemistry Development, Inc., Toronto, Ontario, Canada, www.acdlabs.com, 2008.
2. Bruce, Paula Yukanis. Organic chemistry. fifth. California. Prentice Hall, 2006.
3. Fryhle, CB, and G. Solomons. Organic chemistry. 9th edition. Danvers, MA: Wiley, 2008.
4. McMurray, John. Organic Chemistry. 7th edition. Belmont, California: Thomson Higher Education, 2008.
5. Sadava, Heller, Orion, Purvis, Hillis. The science of biology of life. 8th edition. Sunderland, MA: W.H. Free man, 2008.
6. Vollhardt, K. Peter C., and Neil E. Schore. Organic chemistry. Fifth edition. New York: W. H. Freeman, 2007.

taxpayer

• Winter Zin
• Jim Clark (Chemistry Leader)