If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content

Naming two isobutyl groups systematically

Systematic naming conventions for molecules with two isopropyl groups. Created by Sal Khan.

Want to join the conversation?

  • male robot hal style avatar for user Reto
    i believe the reason to use the special prefix 'bis' is not because you do systematic naming, but because this is a "branched subgroup in paretheses". Otherwise, with your stated logic, you would also have to name the "1,4-dicyclobutyl" as "1,4-bis-cyclobutyl", no?
    (13 votes)
    Default Khan Academy avatar avatar for user
    • spunky sam blue style avatar for user Ernest Zinck
      The special prefix bis is part of systematic naming. Rule R-0.1.4.2 states,
      "The numerical prefixes "bis-", "tris-", "tetrakis-", etc., which, except for "bis-" and "tris-", are derived by adding "kis-" to the simple numerical prefixes …, are used to indicate a multiplicity of substituted substituent prefixes or functional modification terms." I.e., you use bis and tris for substituted substituents.
      (20 votes)
  • blobby green style avatar for user Daniel Thomas
    Which naming system will show up in the real world? How about the MCAT? O-chem class?

    Thanks!
    (7 votes)
    Default Khan Academy avatar avatar for user
    • spunky sam blue style avatar for user Ernest Zinck
      Within a small group, such as a classroom, it is perfectly permissible to use common names. When you have to communicate with the "outside" world, it is preferable to use systematic names. The problem is that different groups of people assign different meanings to the same prefix. For example, isooctane is 2-methylheptane to some people and 2,2,4-trimethylpentane to others.
      I am no expert on the MCAT, but I understand that it emphasizes problem-solving ability rather than regurgitation of facts. I would expect you to have no problem if you are reasonably familiar with either system.
      (13 votes)
  • blobby green style avatar for user Harsha Iyer
    So for the final answer, do we not need to re-alphabetize the compound? When we changed the original name (diisobutyl) to the systematic name bis-( 2 methylpropyl), why don't we make the final answer 1,4-cyclobutyl-5,7-bis(2-methylpropyl)-2-cyclopropylcyclooctane?
    (5 votes)
    Default Khan Academy avatar avatar for user
  • aqualine ultimate style avatar for user sreekar273
    Is it compulsory to use bis or we can even use bi or di ?
    (2 votes)
    Default Khan Academy avatar avatar for user
  • old spice man green style avatar for user Vishav Rajput
    cant the systematic naming be
    1,4-dicyclobutly 5,7-bis(2methlyproply) 2-cycloproply cyclooctane
    im saying this because if you see alphabetically M from methlyproply group comes before P from cycloproply group?? please explain!
    (2 votes)
    Default Khan Academy avatar avatar for user
  • purple pi purple style avatar for user shreya panda
    how do i draw Tri Nitro Tolene.. i dont see hw to break it. meth, eth etc..Tol stand for?
    (1 vote)
    Default Khan Academy avatar avatar for user
    • orange juice squid orange style avatar for user awemond
      Toluene is a benzene ring with a methyl substituent. There are a number of isotopes of trinitrotoluene that are are possible, and you would need to specify numbers before the "trinitro" part to specify a particular isomer. However, unspecified "trinitrotoluene" usually refers to 2,4,6-trinitrotoluene. So in this case you would have a benzene ring with a methyl group attached to carbon #1 on the benzene. The 2nd, 4th, and 6th carbons on the benzene would have a nitro (-NO2) group.
      (4 votes)
  • marcimus purple style avatar for user Maddie
    Is it IUPAC convention to number cycloalkanes according to alphabetic order as Sal does here?
    (1 vote)
    Default Khan Academy avatar avatar for user
    • leaf red style avatar for user Richard
      If there are two more substituents on the ring, the ring carbons are numbered to give the lowest possible numbers for the substituted carbons. The numbering begins with one of the substituted ring carbons and continues in the direction that gives the lowest possible numbers to the other substituents. In the name, the substituents are listed in alphabetical order. When the numbering could begin with either of two substituted ring carbons, begin with the one that has more substituents; otherwise, begin with the one that is first alphabetically.

      Hope that helps.
      (3 votes)
  • blobby green style avatar for user Amy Lee
    Is there a list or chart of names that we would consider for the alphabetical order. For instance, which letter do we consider in bis(methylpropyly)?
    (2 votes)
    Default Khan Academy avatar avatar for user
    • piceratops ultimate style avatar for user Christopher.W.Lambert
      Typically the alphabetical nature of naming is based on the base name and prefixes are ignored. So bis(methylpropyl) would be considered to be alphabetized according to methylpropyl.

      The only time, I believe, that this rule has an exception is when using iso as in isopropyl. That would be alphabetized as isopropyl and not propyl.
      (1 vote)
  • piceratops ultimate style avatar for user Anujith Krishnan
    Why do we add 'bis' in the naming process and when to add it with a name and how to add it
    (1 vote)
    Default Khan Academy avatar avatar for user
    • marcimus purple style avatar for user Aurora_Borealis
      'di' is used when there a two single groups. - Like dimethyl, diethyl etc
      but bis is used when there are two more than one groups... like bis( 1- methyl ethyl)
      because if we use it as di methyl ethyl then that could lead to a possible misconception of thinking of it as two methyl groups and single ethyl group when its actual two single methyl ethyl groups ...
      (2 votes)
  • blobby blue style avatar for user mehrin farjana
    shouldn't all the "di-" be replaced with "bis-"?
    (1 vote)
    Default Khan Academy avatar avatar for user

Video transcript

- [Instructor] In the last video, we named this molecule using the common names for this group right over here and I thought it would be fun to also use- to do the same thing but use the systematic name. So in the last video, we called this isobutyl but if wanted to do it systematically, we would look at this group, we would start at where it is attached to the main backbone, and we would think about the longest chain of carbons from there. So if we start there, we can get one, two, three carbons. So if we're dealing with three carbons, then this is going to be a propyl group, and we would number it one, two, three. And we see on the two carbon of the propyl group, the two carbon of the propyl group, we have a one carbon group right over here, so this is a methyl group branching off the two carbon of the propyl group. So we could call this, we could call this thing the systematic name, instead of calling it isobutyl, we could call it two methyl, that's the methyl group right over there. So let me write this down, two, two methyl propyl, two methyl propyl, two methyl propyl. And so this is the systematic name, and of course there is two of them. This is a two methyl propyl right over here instead of an isobutyl, we'll call it two methyl propyl. And this is another two methyl propyl. So instead of writing, instead of writing the five, seven diisobutyl here, we can instead substitute that with the systematic names. So let's do that. Let me copy and paste everything else that comes before it. So let me copy, copy and paste it. Whoops. Whoops, I'm in the wrong layer of my program. Let me go one layer down. So let me copy and paste it again. Copy and paste, there we go. So I got that part. But now I'm going to write this part differently. So we still have stuff, we still- it's still on the five carbon and the seven carbon of our main chain. So five comma seven, and we have two of'em, but when we're using systematic naming, we won't say di- this thing, instead we say bis-. So five comma seven bis, that says, "Hey, we've got two of what I'm about to say." Bis- this thing. So let me copy, dude, that's in a different layer. Let me copy and let me paste that. Bis- this stuff right over here, and then, of course, we have cyclooctane. And then, of course, we have cyclooctane, and we are done. We have named it systematically as well.