leah here from leh Versailles calm and in this video I will show you how to name alkynes using the IU PAC system before we can name alkynes you have to know how to recognize them in a molecule an alkyne occurs when you have two pi bonds between the same two set of carbons also known as a carbon two carbon triple bond the hybridization of the carbon that holds the alkyne is SP which means that it has a bond angle of 180 degrees and the shape of the molecule will be linear let's try a simple alkyne for example C Triple C single bound to H this is a sign commonly called acetyl lean if you compare this to a two carbon alkane will have the H C single bound CH but we also have two additional sets of hydrogen's as we place each PI bond we have to remove two hydrogen's which gives the alkyne a hydrogen deficiency index of two and the formula of cnh2n -2 this is compared to the formula of an alkane for cnh2n plus 2 due to the difference of four hydrogen's when drawing an alkyne in lime structure remember that the bond angle is 180 degrees people will often draw an alkyne almost like an alkane by adding two bonds but this is incorrect and this is because the alkyne is linear and has to be drawn as a straight line when reading this structure though don't forget that the triple bond starts and ends on two carbons but you also have two additional carbons on the end of the chain to name an alkyne you follow the same rules that you would for standard I you pack naming and that means we first identify the parent chain given that the alkyne occurs in the middle of the molecule I can start numbering from the right or the left and I have a total of 4 carbons giving me a first name of Bute because i have a triple bond in the molecule i get a last name of YN e where ein i place number 2 in front of the IM to specify where the triple bond occurs on the molecule and this gives me a final name of 2-butene let's try another example for this example recognize that we have a terminal alkyne because the triple is at the end of the molecule I start by highlighting the parent chain when the alkyne is your highest priority you start numbering from the side that will give it the lowest number they start numbering from the left and get a total of five for our first name of pent since the triple bond occurs on number one I have one line for a final name of one pen time for this example I have a substituted alkyne and once again I start by highlighting my parent chain I have the option of numbering from the left where I hit a methyl group at carbon two or numbering from the right where I hit the alkyne at carbon two when you have a substituent and a triple bond that both have the same number the substituent gets highest priority and that means I have to start numbering from the left seven carbons in my parent chain gives me a first name of Hecht hitting my triple bonded carbon five gives me a last name of five ein and my methyl group substituent on carbon 2 gives me two methyl putting the name together I have two methyl five hep time a dying is not as scary as it sounds it simply means that you have to carbon the carbon triple bonds on the same molecule will use this molecules an example and once again we start by highlighting the parent chain in this case I have a terminal alkyne on the left and so we start numbering from the left to get a total of seven carbons for a first name of HEPT since I have two triple bonds occurring on carbon 1 and carbon 5 I start with the last name of dine to show that I have two triple bonds but I also have to include both numbers giving me 1 comma 5 putting this name together with the numbers preceding the dine I get kept 1 5 dine if I choose to put the numbers in the front of the molecule I have something interesting occur I have 1 5 Hecht dine but because T and D are both consonants and don't flow together I have to add the letter A so I get 1 5 hepta dine to make the molecule read better in the next video we'll look at how to name a molecule that has both an alkene and an alkyne in the same molecule are you struggling with organic chemistry are you looking for information to guide you through the course and help you succeed if so download my ebook 10 secrets to acing organic chemistry using the link below or visit layer 4 si.com slash or go secrets that's so our geo secrets for information regarding online tutoring visit layovers sicom slash or yo tutor that's oor geo tutor if you enjoyed this video please give it a thumbs up and even share it with a friend or two if you have any questions regarding this video leave a comment below or contact me through my facebook page at facebook.com slash layovers site there will be many related videos posted over the course of the semester so go ahead and click the subscribe button to insure that you don't miss out