The understandable notes- Carbon and its compounds, Class 10, Part-3

 NOMENCLATURE OF ORGANIC COMPOUNDS

The organic compounds are named by using a proper method and rules. These rules are formed by IUPAC ( International union of pure and applied chemistry). There are also common names of compounds but they differ in different regions and hence a systematic method of naming is formed which is same across globe.

( Organic compounds ki naming ka ek proper tarika hota hai. Ye method IUPAC ne banaye hai. Pehle har compound ka local name hota tha lekin fir iupac ne ek proper naming technique banayi hai jis se har compound ka ek unique name ho jo har jagah valid ho. Ab nomenclature vaise to apne aap mai bahut bada topic hai jab maine 11 me padha tha to 7 din mai complete hua tha lekin tumhari class mai sirf 2 ghante ka hai tension mat lo. Haan aur is part mai notebook jaroor lekar baithna.)

The process of naming the compounds is i  the following sequence.

In the diagram you can see many terms, let us understand the meaning of each term separately. 

( Dekho jo compounds ki naming hoti hai vo kuch is sequence mai hoti hai jo upar dikhai de rhi hai. Ab is diagram mai kai terms hai jo aapke liye nayi hai to har term ko ek ek karke samajhte hai. )

Word Root-  This tells about the number of carbon in main chain of compound. The main chain of any compound is that chain which contains the maximum number of carbon. Depending on the number of carbon in the main chain the word root is decided, the following pic represents the word root for carbon upto 12.

( To sabse jyada important term hai word root jo ki nomenclature ke liye bahut important hai. Word root hame ye batata hai ki compound ki main chain mai kitne atoms hai carbon ke. Ek baat yaad rakhna ki word root sirf main chain ke number of atom batata hai na ki pure compound ke. Kyonki pure compound mai branching bhi ho sakti hai. Ab ye jo upar figure di hui hai ise yaad krlo kaise bhi kyonki iske bina to nomenclature nhi aaega. Vaise aage bhi bahut kuch hai jo yaad krna padega kyonki organic chemistry ek yaad krne wala subject hai. Aur samajhne wala bhi. Haan to is table to yaad kr lo chahe likh kar chahe bol kar bas kr lo.)

Primary prefix (1°Prefix)

It tells us about that that the compound is cyclic or straight. It is placed before the word root. If the compound is straight then it remains as it is but if the compound is cyclic then a word "cyclo" is written before the word root.

( Haan to uske baad aata hai primart prefix jo hume ye batata hai ki compound cyclic hai ya fir straight. Dekho carbon ke compounds straight bhi ho sakte hai, branched bhi ho sakte hai aur ring like structure bhi ho sakte hai. Baki iski koi jarurat aur jarurat nhi hai. )

Secondary Prefix ( 2° Prefix )

It tells us about the branches and substituents attached to main chain. Substituents can be halogens and branches is of carbon.

( Iska kaam hai ki ye batata hai ki main chain se kitni aur kaha branches hai aur koi substituents bhi hai. )

Primary Suffix ( 1° Suffix ) 

It tells us about that the compound is double bonded, single bonded or triple bonded.

If the compound is single bonded then we use the primary suffix- ane.

Like- methane

If the compound is double bonded then we use the Suffix- ene.

Like- ethene

If the compound is triple bonded, then we use the suffix - yne.

Like- ethyne.

( Primary suffix hume ye batate hai ki compound double bond wala hai, single bond wala hai, ya fir triple bond wala. Ab agar single bond hai to hum ane use krte hai. Agar double bond hai to hum use krte hai ene, aur agar triple bond hai to hum yne use krte hai.)

Secondary Suffix 

It tells us about the main functional group attached to compound. In a compound there can be many functional groups but secondary suffix tells that which functional group is principal.

( Ab ye hume batate hai ki compound mai sabse important ya dominant functional group konsa hai. Ek compound mai kai functional group ho  sakte hai lekin secondary suffix hume ye batate hai ki dominant functional group konsa hai.)  

Rules for nomenclature of organic compounds

1. Select the longest possible continuous chain of carbon in the compound. The chain can be straight ot bent.

( Sabse pehle carbon ki sabse lambi chain ko identify krna hoga. Kaise ye niche samajh aaega )

Niw find the longest chain of carbon in the compound.

( Ab is figure mai carbon ki longest chain dhundo. Yaad rakhna chain continuous honi chahiye aur kahi se bhi shuru ho sakti hai. To ab mai niche sahi chain banakar represent krunga aur sath mai vo bhi jinhe maximum bacho nai select kiya hoga. )

So the longest chain in the compound will have 10 atoms of carbon.

( To sabse lambi chain is compound mai ye wali hogi jo maine draw kari hai. Vaise draw to nhi kari pr likhne mai kya jata hai. To chalo ek baar aap sabka answer.bhi match kr lete hai ye niche wala hoga. )

This is wrong because it has only nine electron while the maximum number of atoms possible in the longest chain is 10.

(  To dekho kyonki jo longest chain hai usme 10 atom aa sakte hai aur ye sirf 9 atoms ko hi cover kr pa rahi hai isi liye ye correct nhi hai.)

2. Number the Carbon Atoms

Number the carbon atoms in the parent chain, starting from the end nearest to a substituent or functional group.

If there are no substituents, number from the end closer to a double/triple bond or a functional group.

( Ab dekho parent chain to identify krne ke baad dusra kaam aata hai numbering krna. Ab numbering krne ke liye bhi ek criteria hota hai. Numbering us taraf se hoti hai jisme jo substituents hote hai vo lowest number par hote hai. Agar substituents na ho to ye check krte hai ki double group ya triple group ko lowest number mile. Aur teesri chiz hai functional group. Ab inki bhi  ek priority level hoti hai jo niche diagram mai dikhai gayi hai).

It means that if a substituent and double bond will get same number is counted from opposite side then we count from double bond or triple bond side and similarly if we get functional group from one side and double bond from another side then we number from functional group side. It implies that functional has the most priority all over.

( Ab ye jo diagram hai jisme ye dikhaya gaya hai ki functional group ki priority jyada hoti hai as compared to double or triple bond aur in double bond ya triple bond se jyada functional group ki priority hoti. Ab soch kar batao ki agar ek side pr chalne se ek substituent mile or dusri side par chalne se functional group to konsi side se numbering hogi. Ab jo bache ye soch rhe hai ki functional group ki priority kyonki double or triple bond se jyada hoti hai isiliye substituent se bhi jyada hongi aur isi liye numbering functional  group ki taraf se hongi to bilkul shi soch rhe hai. Ab dekho ye topic itna complex to nahi hai pr notes ke through ise samjhna bahut mushkil kaam hai. Isi liye pehle har rule ko explain kr rha hu. )

3) Now add word root.

( Sabse pehle word root decide karo. Ye kaise hogi aage samajh aayega.) 

4) Then add prefix and suffix.

( Fir prefix or suffix ko add karo. Chalo kaise krte hai ye step by step samajhte hai.)

Naming of Alkanes containing branches only

1)Select the longest possible continuous chain of carbon atom.

(  Ye to piche bhi samjhaya tha. Bas vahi hai.)

2) Now select the longest chain in such a way that it gets the maximum number of branches.

( Ab ye koshish karo ki lingest chain mai bhi sanse jyada branches ho. Yani ki sabse pehle to longest chain identify karo. Uske baad agar longest chain kai tarike se ban sakti hai to ye koshish karo ki vo chain select karo jisme branches of carbon maximum vo or branches ke andar subbranching to avoid krne ki koshish karo. )

Try to find the longest chain of carbon in the given compound. Take into consideration that we need to select that chain in which maximun number of branches occur.

 ( Haan to is compound mai longest chain dhundhi carbon ki aur dhyan rakhna ki hume )

There are two possibilities of deciding the longest chain. 

Or

B

Now, which of the above pics are correct.

First rule is to select longest chain of maximum carbon but here both chains have eight carbon so this rule is not enough to select the final chain. Now apply the second rule, which implies that this chain should contain maximum number of branches.

Chain A contains 3 branches with internal branching in one branch. 

And chain B also contains eight atoms but it contains four branching and there is no internal branching so we have to select this chain.

( to sabse pehla rule hai ki longest chain select karo jismemaximum carbon atoms ho. Ab ye krne ke do tarike hai. Kon kon se te upar dono diagrams mai dikhaye gaye hai. Aur uske baad ye rule dono mai tie ho jata hai. Fir hume ye sochna hai ki kis chain mai maximum number of branches hai aur hume sub braching yani branches ki braches ko avoid krna hai. Yani ki hume parent chain ko is tarah se select krna hai jisse braches ka number to maximum ho pr internal branching na ho. Haan to figure B mai vo condition meet ho jati hai.)

2) Now number the compound after selecting the parent chain.

( Ab parent chain ko ide tify krna jitna bada kaam dikh raha hai itna bada hai nhi. To iske baad numbering krne ki bari aati hai. Ab numbering kaise kare. Dekho parent chain ki numbering kisi ek end se shuru hokar dusre end tak jati hai. Yani ki jo compound maine upar use kiya hai uski numbering do tarike se ho sakti hai.)

A

There are two possible counting. 

When we select numbering as suggested in figure A the  we got first substituent on position 4. Then we got second and third one  one on position 6 and finally fourth substituent on position on 7.

Bur when we number the compound as suggested in figure two or B then we got the first substituent  on position 2.

As we have to number any compound to get lowest locant, we prefer numbering as suggested in figure B.

( Ab parent chain select krne ke baad numbering krne ki bari aati hai. Ye to common sense hai ki numbering do tarike se hi ho sakti hai. Ya to ek end se dusre end ya fir dusre end se pehle end. Haan to agar is specific compound ki baat kare to is compound mai agar hum numbering pehli pic wali side se krte hai to hume pehla substituent fourth number pr milta hai. Itna krte ho ruk jao or dusri taraf se numbering start krdo. Ab agar opposite side se numbering kare to pehla substituent 2 position par mil jayega. Haan to is case mai hum second wali numbering prefer karenge. Sabse pehle hume is baat ka dhyan rakhna hai ki pehla substituent kis taraf se numbering krne par pehle milega. Vaise to ise lowest set of locants bhi bolte hai pr kya jarurat hai yaad krne ki bas concept clear hona chahiye. Chalo parent chain dhund li aur numbering kr li, iske baad pramukh karyakram shuru hota hai vo hai naming ka.)

3) Identify the substituent and their positions.

( iske baad ye dekhna hai ki substituent kaha kaha pr present hai aur kon kon se present hai. Ab sare rules isi compound ke aspect mai samjha dunga uske baad tum practice khud kr lena aur agar koi doubt ho to mujhe insta pr comment kr dena. )

If a single hydrogen is removed from a alkane and bonded to compound like a branch, then we delete the last "ane" and add "yl". Means id methane like group is attached to compound then its name will be methyl. Now see the diagram carefully.

( agar alkane to ek branch ki tarah treat kara jaye to unhe alkyl kehte hai. Jaise ki methane ka methyl or ethane ka ethyl. )

This is the proper diagram of the given compound. Now if we consider the parent chain and then name the first substituent then the first substituent is placed on position second which is methyl. On the third position the substituent placed is ethyl and on the third position there is also one more substituent which is methyl. And on the 5th position there is methyl.

( Ab parent chain decide kr li, numbering decide kr li to uske baad turn aati hai substituent ko identify krne ki. Ye jo upar diagram diya hai ye proper diagram hai matlab ki aise hi compound ko tumhe show kiya jayega. Ab dekho ise master krne ke liye jarori hai practice to bas 2-3 ghante nomenclature ki practice kr lo. Further class 11 mai ye nomenclature ek din mai bhi khatam nahi hoga. Abhi jitna hai utna kr lo. Haan to hume ye to pata chal hi gaya ki is compound ke andar kya kya hai to bas ab naming shuru krte hai is figure ki help se.)

First we have to write secondary prefix which tells us about branches and substituents.

So let us name the substituent 

At position 2 there is methyl so it name would be,  2- methyl

At position 3 there are two substituents which are ethyl and methyl, so their name will be ,

3- methyl and 3- ethyl.

Now there is a rule to write the substituents, substituents are always named alphabetically, but we doesn't consider di and tri on alphabetical  selection.

So the naming of substituent will be as follows

3-ethyl 2-methyl 3-methyl 5-methyl

As methyl is present on three position this is written as

"3-ethyl 2,3,5- trimethyl."

Keep one thing in mind that nomenclature is a name and there is no gaping in name, it means that no letter except the first one will capital and there is no spacing in the name. Just example if Ramchandar is a name of some person than if will nor we written as RamChandaR or R am chanda r.

If there are two methyl then we write dimethyl and as d comes alphabetically first so di should have to come first but as i had said earlier that we doesn't  consider di and tri while selecting alphabetically so even if there are only two methyl groups ethyl comes first. 

(To nomenclature mai sabse pehle aata hai secondary suffux likhna. To secondary suffix hume ye batata hai ki substituent kaha kaha pr laga hai aur kon kon sa. To humne sabse pehle ye dekha ki substituent kaha par present hai or kon kon sa or uske baad humne individually har substituent ko unki position ke sath likh liya. Ab sare substituent ko dhyan se observe krna aur jo substituent alphabetically first aata ho use sabse pehle likhenge. Ab agar do ya teen same substituent ho to unhe positions likhkar fir unke aage di ya tri laga diya jata hai. Aur alphabetically select krne ke liye hum di or tri ko consider nhi krte. Iska matlab dimethyl ethyl se pehle nhi aaega. Haan to dusri, teesri aur paanchvi position par methyl hai to ise baar baar likhne se badhiya ek baar hi likh do. To sari positions likho or iske baad jitni positions pr present haiutni positions par di ya tri apne hisab se likh do. Aur ek baat ki nomenclature ek naam hai aur naam ke beech mai koi bhi alphabet capital nahi hoga aur name ke beech mai jyada spacing nhi hongi. Aur commas ka use tab hota hai jab same group kai positions par present ho.)

After that there is turn to write primary prefix which tells us about that the compound is cyclic or straight. As the compound is straight so there is no need to write primary prefix.

( Haan to is compound mai primary prefix ka koi kaam hi nahi hai to iski baat krke bhi koi fayda nahi hai.)

Then it is turn to write word root. Word root tells us about the number of carbon atoms in main chain or parent chain or longest continuous chain. As in this compound the maximum number of carbon in parent chain is 8, si the word root will be oct. And after that there is turn to write primary suffix which tells us about that the compound in aingle bonded, double bonded or triple bonded.

As this compound only contains single bond the primary suffix will be ane. So the complete name of the longest chain will be octane.

( Ab uske baad bari aati hai word root likhne ki. Word root hume batata hai ki parent chain mai kitne atoms hai. Jo mahan log ye soch rahe hai ki mai baad baar har chiz ko define kyo kar raha hu to isi liye ki tumhe ye sab bilkul rat jaye. Ki kis chix ko kya kehte hai hai aur kiska kya kaam hota hai. To jaise is compound mai 8 atom present hai to iski word root oct hogi aur uske baad primary suffix ki turn asti hai jo hume batata hai ki compound mai sirf single bond hai ya fir double bond aur triple bond bhi hai aur agar hai to kaha kaha hai. To is hisab se oct ke baad primary suffix ane lagega jiske baad is compound ka name octane padega. )

Then there is turn to write secondary suffix. It tells us about functional group. But as there is no functional group present in the compound so there is no need to write secondary suffix.

So the name of the compound will be

"3-ethyl 2,3,5-trimethyl octane"

( haan to uske baad secondary suffix likhne ki turn aati hai. Ab secondary suffix ka use to functinal group ke liye hota hai or kyunki is compound mai koi functional group hi nhi hai to ise likhne ka koi matlab hi nhi banta. Haan to chalo ek bala to tali. Ab itne sare rules likh  diye to ek aadha question bhi practice kr lo. Agar iski worksheet chahiye to bata dena. Vo bhi bana denge.)

Some more substituent with their prefix 

Now name the following compound

In this compound you can find parent chain easily but face a problem while assigning number to compound. Because on numbering from both side we get our first substituent at position. Then, we have to see where we get second substituent. If we number from left side then we get second substituent at position three but if we number from right hand side then we get second substituent at position 5, so we now prefer numbering from left hand side.

( Ab is question mai ek problem aayegi ki dono taraf se substituent same position par mil rahe hai. Is liye hum second substituent ko dekhenge. Lekin agar second substituent hi na ho fir, fir kya hum jo alphabetically pehle aaega use priority de denge. Ek baat yaad rakhna ki agar koi bhi group substituent ki tarah treat ho raha hai to inki sabki priority same hongi. Farak nhi padta ki vo alkyl ho, halogen ho, alkenyl ho vagera. Haan to is compound mai ye ek chota se doubt tha jo maine clear kr diya ab iski naming karo. Mai sirf name likh raha hu.)

The name of the compound will 

5-fluoro 3,3-dimethylheptane.

If you are thinking that numbering is done by giving priority to methyl groups as two groups are attached to same position but in name why fluoro is written first so in naming we generally write the substituents alphabetically. As F comes before m so it is written before and i have said it earlier that we doesn't consider di, and tri while writing alphabetically.

( Haan to is compound ka kya naam hai vo bhi likh diya or ek baat ki substituents ko hum alphabetically hi likhte hai unki positions ke sath mai. Ab jaise methyl ki poaition 3 thi or fluoro ki 5 tab bhi hum fluoro ko pehle likhenge. Ab agar koi ye soch raha hai ki dimethyl mai to d consider hokar fluoro se pehle aa jayega to hum di or tri ko consider nhi krte. To simple alkane with branching and substituent ko to humne padh liya ab bari aati hai alkenes or functional group ko study krne ki jo hum next part mai karenge. Vo part kafi easy hoga agar aapka basic clear hai to is part ko achi tarah se samajh lena.)