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Organic Chemistry
12 Jul 2007 20:12:30 IST
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Hrishikesh Gurjar
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12 Jul 2007 21:21:40 IST
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you can get the basic names of alkanes upto say decane. then other groups are easy make a chart and read it anytime ur free. i got it same way. am in 12th now!!
put the chart where u can easily read it!!
rate me if u liked it.....
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12 Jul 2007 22:49:02 IST
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ya as every body says here dat only prctise is the thng vch can make u perfect in field of nomenclature,,,,,,,,,,,,,,,bt wat i want to say is this is first of all take a general introduction of sigma and pie bonds,carbon covalency,naming of gen. alkanes,alkenes and alkynes and den set the functional groups as thier structure, prefix and sufix........after taking all these thngs in ur glance............dnt take ny of the book.............if u knw the rules.........if u dnt knw the rules then u should prefer book only for rules den strat making a carbon chain according to ur choice.........start frm single chain and do it urself.........and then get it checked by ur teachers..........and by using his method i thnk u can make ur nomenclature side vry strong as i learned it in class IX and i had chosen the way vch i told u ............even do u knw i used to make drawing by using carbon chain and so many thngs...............so try this............and if u r having ny doubt abt rules u can ask me here only ..............i m always here to help u............
in a conclusion i want to say dat.........MAKE ALL THE RULES CLEAR FIRST THEN START MAKING COMPOUNDS FRM URSELF AND TRY TO GV NAME TO IT.........................BEST OF LUCK TO U
As i knw u hav the will power to do it.............
12 Jul 2007 23:14:36 IST
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are u talking about specific nomenclature (as in u r given all the carbon compounds and u r asked to mug it ?) or like u open a chapter and there u cant understand nomenclature ??
basically...... u dont have to study nomenclature specially........atleast i dont and so do my friends.....when u open a chapter.........the first part is usually nomenclature......tab ka tab kar lena.......aisa alag chapter padhna is not feasible.....if its there in ur portion......then just go thru some NCERT 12th ka organic chem and nomenclature given for specific compounds (like for eg. Ketones....)
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basically...... u dont have to study nomenclature specially........atleast i dont and so do my friends.....when u open a chapter.........the first part is usually nomenclature......tab ka tab kar lena.......aisa alag chapter padhna is not feasible.....if its there in ur portion......then just go thru some NCERT 12th ka organic chem and nomenclature given for specific compounds (like for eg. Ketones....)
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13 Jul 2007 13:07:21 IST
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The IUPAC nomenclature system is a set of logical rules devised and used by organic chemists to circumvent problems caused by arbitrary nomenclature. Knowing these rules and given a structural formula, one should be able to write a unique name for every distinct compound. Likewise, given a IUPAC name, one should be able to write a structural formula. In general, an IUPAC name will have three essential features:
? A root or base indicating a major chain or ring of carbon atoms found in the molecular structure.
? A suffix or other element(s) designating functional groups that may be present in the compound.
? Names of substituent groups, other than hydrogen, that complete the molecular structure.
? A suffix or other element(s) designating functional groups that may be present in the compound.
? Names of substituent groups, other than hydrogen, that complete the molecular structure.
Alkanes
Hydrocarbons having no double or triple bond functional groups are classified as alkanes or cycloalkanes, depending on whether the carbon atoms of the molecule are arranged only in chains or also in rings. Although these hydrocarbons have no functional groups, they constitute the framework on which functional groups are located in other classes of compounds, and provide an ideal starting point for studying and naming organic compounds. The alkanes and cycloalkanes are also members of a larger class of compounds referred to as aliphatic. Simply put, aliphatic compounds are compounds that do not incorporate any aromatic rings in their molecular structure.
The following table lists the IUPAC names assigned to simple continuous-chain alkanes from C-1 to C-10. A common "ane" suffix identifies these compounds as alkanes. Longer chain alkanes are well known, and their names may be found in many reference and text books. The names methane through decane should be memorized, since they constitute the root of many IUPAC names. Fortunately, common numerical prefixes are used in naming chains of five or more carbon atoms.
The following table lists the IUPAC names assigned to simple continuous-chain alkanes from C-1 to C-10. A common "ane" suffix identifies these compounds as alkanes. Longer chain alkanes are well known, and their names may be found in many reference and text books. The names methane through decane should be memorized, since they constitute the root of many IUPAC names. Fortunately, common numerical prefixes are used in naming chains of five or more carbon atoms.
| Name | Molecular Formula | Structural Formula | Isomers | Name | Molecular Formula | Structural Formula | Isomers | |
|---|---|---|---|---|---|---|---|---|
| methane | CH4 | CH4 | 1 | hexane | C6H14 | CH3(CH2)4CH3 | 5 | |
| ethane | C2H6 | CH3CH3 | 1 | heptane | C7H16 | CH3(CH2)5CH3 | 9 | |
| propane | C3H8 | CH3CH2CH3 | 1 | octane | C8H18 | CH3(CH2)6CH3 | 18 | |
| butane | C4H10 | CH3CH2CH2CH3 | 2 | nonane | C9H20 | CH3(CH2)7CH3 | 35 | |
| pentane | C5H12 | CH3(CH2)3CH3 | 3 | decane | C10H22 | CH3(CH2)8CH3 | 75 |
Some important behavior trends and terminologies:
(i) The formulas and structures of these alkanes increase uniformally by a CH2 increment.
(ii) A uniform variation of this kind in a series of compounds is called homologous.
(iii) These formulas all fit the CnH2n+2 rule. This is also the highest possible H/C ratio for a stable hydrocarbon.
(iv) Since the H/C ratio in these compounds is at a maximum, we call them saturated (with hydrogen).
(ii) A uniform variation of this kind in a series of compounds is called homologous.
(iii) These formulas all fit the CnH2n+2 rule. This is also the highest possible H/C ratio for a stable hydrocarbon.
(iv) Since the H/C ratio in these compounds is at a maximum, we call them saturated (with hydrogen).
Beginning with butane (C4H10), and becoming more numerous with larger alkanes, we note the existence of alkane isomers. For example, there are five C6H14 isomers, shown below as abbreviated line formulas (A through E):
Although these distinct compounds all have the same molecular formula, only one (A) can be called hexane. How then are we to name the others?
The IUPAC system requires first that we have names for simple unbranched chains, as noted above, and second that we have names for simple alkyl groups that may be attached to the chains. Examples of some common alkyl groups are given in the following table. Note that the "ane" suffix is replaced by "yl" in naming groups. The symbol R is used to designate a generic (unspecified) alkyl group.
| Group | CH3? | C2H5? | CH3CH2CH2? | (CH3)2CH? | CH3CH2CH2CH2? | (CH3)2CHCH2? | CH3CH2CH(CH3)? | (CH3)3C? | R? |
| Name | Methyl | Ethyl | Propyl | Isopropyl | Butyl | Isobutyl | sec-Butyl | tert-Butyl | Alkyl |
IUPAC Rules for Alkane Nomenclature 1. Find and name the longest continuous carbon chain. 2. Identify and name groups attached to this chain. 3. Number the chain consecutively, starting at the end nearest a substituent group. 4. Designate the location of each substituent group by an appropriate number and name. 5. Assemble the name, listing groups in alphabetical order. The prefixes di, tri, tetra etc., used to designate several groups of the same kind, are not considered when alphabetizing. |
For the above isomers of hexane the IUPAC names are: B 2-methylpentane C 3-methylpentane D 2,2-dimethylbutane E 2,3-dimethylbutane
Halogen substituents are easily accomodated, using the names: fluoro (F-), chloro (Cl-), bromo (Br-) and iodo (I-). For example, (CH3)2CHCH2CH2Br would be named 1-bromo-3-methylbutane. If the halogen is bonded to a simple alkyl group an alternative "alkyl halide" name may be used. Thus, C2H5Cl may be named chloroethane (no locator number is needed for a two carbon chain) or ethyl chloride.
Cycloalkanes
Cycloalkanes have one or more rings of carbon atoms. The simplest examples of this class consist of a single, unsubstituted carbon ring, and these form a homologous series similar to the unbranched alkanes. The IUPAC names of the first five members of this series are given in the following table. The last (yellow shaded) column gives the general formula for a cycloalkane of any size. If a simple unbranched alkane is converted to a cycloalkane two hydrogen atoms, one from each end of the chain, must be lost. Hence the general formula for a cycloalkane composed of n carbons is CnH2n.
| Name | Cyclopropane | Cyclobutane | Cyclopentane | Cyclohexane | Cycloheptane | Cycloalkane |
|---|---|---|---|---|---|---|
| Molecular Formula | C3H6 | C4H8 | C5H10 | C6H12 | C7H14 | CnH2n |
| Structural Formula |  |  |  |  |  | (CH2)n |
| Line Formula |  |  |  |  |  |  |
Substituted cycloalkanes are named in a fashion very similar to that used for naming branched alkanes. The chief difference in the rules and procedures occurs in the numbering system. Since all the carbons of a ring are equivalent (a ring has no ends like a chain does), the numbering starts at a substituted ring atom.
IUPAC Rules for Cycloalkane Nomenclature 1. For a monosubstituted cycloalkane the ring supplies the root name (table above) and the substituent group is named as usual. A location number is unnecessary. 2. If the alkyl sustituent is large and/or complex, the ring may be named as a substituent group on an alkane. 3. If two different substituents are present on the ring, they are listed in alphabetical order, and the first cited substituent is assigned to carbon #1. The numbering of ring carbons then continues in a direction (clockwise or counter-clockwise) that affords the second substituent the lower possible location number. 4. If several substituents are present on the ring, they are listed in alphabetical order. Location numbers are assigned to the substituents so that one of them is at carbon #1 and the other locations have the lowest possible numbers, counting in either a clockwise or counter-clockwise direction. 5. The name is assembled, listing groups in alphabetical order and giving each group (if there are two or more) a location number. The prefixes di, tri, tetra etc., used to designate several groups of the same kind, are not considered when alphabetizing. |
Small rings, such as three and four membered rings, have significant angle strain resulting from the distortion of the sp3 carbon bond angles from the ideal 109.5º to 60º and 90º respectively. This angle strain often enhances the chemical reactivity of such compounds, leading to ring cleavage products. It is also important to recognize that, with the exception of cyclopropane, cycloalkyl rings are not planar (flat).
Hydrocarbons having more than one ring are common, and are referred to as bicyclic (two rings), tricyclic (three rings) and in general, polycyclic compounds. The molecular formulas of such compounds have H/C ratios that decrease with the number of rings. In general, for a hydrocarbon composed of n carbon atoms associated with m rings the formula is: CnH(2n + 2 - 2m). The structural relationship of rings in a polycyclic compound can vary. They may be separate and independent, or they may share one or two common atoms. Some examples of these possible arrangements are shown in the following table.
Examples of Isomeric C8H14 Bicycloalkanes
| Isolated Rings | Spiro Rings | Fused Rings | Bridged Rings |
|---|---|---|---|
| No common atoms | One common atom | One common bond | Two common atoms |
 |  |  |  |
13 Jul 2007 13:11:28 IST
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Alkenes and Alkynes
Alkenes and alkynes are hydrocarbons which respectively have carbon-carbon double bond and carbon-carbon triple bond functional groups. The molecular formulas of these unsaturated hydrocarbons reflect the multiple bonding of the functional groups:
| Alkane | R?CH2?CH2?R | CnH2n+2 | This is the maximum H/C ratio for a given number of carbon atoms. |
|---|---|---|---|
| Alkene | R?CH=CH?R | CnH2n | Each double bond reduces the number of hydrogen atoms by 2. |
| Alkyne | R?C?C?R | CnH2n-2 | Each triple bond reduces the number of hydrogen atoms by 4. |
IUPAC Rules for Alkene and Cycloalkene Nomenclature 1. The ene suffix (ending) indicates an alkene or cycloalkene. 2. The longest chain chosen for the root name must include both carbon atoms of the double bond. 3. The root chain must be numbered from the end nearest a double bond carbon atom. If the double bond is in the center of the chain, the nearest substituent rule is used to determine the end where numbering starts. 4. The smaller of the two numbers designating the carbon atoms of the double bond is used as the double bond locator. If more than one double bond is present the compound is named as a diene, triene or equivalent prefix indicating the number of double bonds, and each double bond is assigned a locator number. 5. In cycloalkenes the double bond carbons are assigned ring locations #1 and #2. Which of the two is #1 may be determined by the nearest substituent rule. 6. Substituent groups containing double bonds are: H2C=CH? Vinyl group H2C=CH?CH2? Allyl group |
IUPAC Rules for Alkyne Nomenclature
1. The yne suffix (ending) indicates an alkyne or cycloalkyne.
2. The longest chain chosen for the root name must include both carbon atoms of the triple bond.
3. The root chain must be numbered from the end nearest a triple bond carbon atom. If the triple bond is in the center of the chain, the nearest substituent rule is used to determine the end where numbering starts.
4. The smaller of the two numbers designating the carbon atoms of the triple bond is used as the triple bond locator.
5. If several multiple bonds are present, each must be assigned a locator number. Double bonds precede triple bonds in the IUPAC name, but the chain is numbered from the end nearest a multiple bond, regardless of its nature.
6. Because the triple bond is linear, it can only be accomodated in rings larger than ten carbons. In simple cycloalkynes the triple bond carbons are assigned ring locations #1 and #2. Which of the two is #1 may be determined by the nearest substituent rule.
7. Substituent groups containing triple bonds are:
HC?C? Ethynyl group
HC?CH?CH2? Propargyl group
2. The longest chain chosen for the root name must include both carbon atoms of the triple bond.
3. The root chain must be numbered from the end nearest a triple bond carbon atom. If the triple bond is in the center of the chain, the nearest substituent rule is used to determine the end where numbering starts.
4. The smaller of the two numbers designating the carbon atoms of the triple bond is used as the triple bond locator.
5. If several multiple bonds are present, each must be assigned a locator number. Double bonds precede triple bonds in the IUPAC name, but the chain is numbered from the end nearest a multiple bond, regardless of its nature.
6. Because the triple bond is linear, it can only be accomodated in rings larger than ten carbons. In simple cycloalkynes the triple bond carbons are assigned ring locations #1 and #2. Which of the two is #1 may be determined by the nearest substituent rule.
7. Substituent groups containing triple bonds are:
HC?C? Ethynyl group
HC?CH?CH2? Propargyl group
Benzene Derivatives
The nomenclature of substituted benzene ring compounds is less systematic than that of the alkanes, alkenes and alkynes. A few mono-substituted compounds are named by using a group name as a prefix to "benzene", as shown by the combined names listed below. A majority of these compounds, however, are referred to by singular names that are unique. There is no simple alternative to memorization in mastering these names.
Two commonly encountered substituent groups that incorporate a benzene ring are phenyl, abbreviated Ph-, and benzyl, abbreviated Bn-. These are shown here with examples of their use. Be careful not to confuse a phenyl (pronounced fenyl) group with the compound phenol (pronounced feenol). A general and useful generic notation that complements the use of R- for an alkyl group is Ar- for an aryl group (any aromatic ring).
When more than one substituent is present on a benzene ring, the relative locations of the substituents must be designated by numbering the ring carbons or by some other notation. In the case of disubstituted benzenes, the prefixes ortho, meta & para are commonly used to indicate a 1,2- or 1,3- or 1,4- relationship respectively. In the following examples, the first row of compounds show this usage in red. Some disubstituted toluenes have singular names (e.g. xylene, cresol & toluidine) and their isomers are normally designated by the ortho, meta or para prefix. A few disubstituted benzenes have singular names given to specific isomers (e.g. salicylic acid & resorcinol). Finally, if there are three or more substituent groups, the ring is numbered in such a way as to assign the substituents the lowest possible numbers, as illustrated by the last row of examples. The substituents are listed alphabetically in the final name. If the substitution is symmetrical (third example from the left) the numbering corresponds to the alphabetical order.
Here are a few sites where you can learn nomenclature
http://www.chem.ucalgary.ca/courses/351/orgnom/index.html
http://www.acdlabs.com/iupac/nomenclature/
http://en.wikipedia.org/wiki/IUPAC_nomenclature_of_organic_chemistry
http://www.chem.qmul.ac.uk/iupac/
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