 properties of alkyne. C2 to C4 carbon exist in gases state C5 to C12 is liquid as C13 solid. For this also boiling point is directly proportional to the molecular mass. Boiling point, melting point is directly proportional to the Sir, is the even-ought thing valid even here? The even-ought thing for melting point? Yes, that is also clear. What is the even-ought thing for melting point? Melting point has an irregular trend, not like it will increase with molecular mass. Like C18 is more than C17. It's because of the packing of the molecule, more packing, not due to the melting point. So, melting point like boiling point does not have a regular trend. Okay, that's it. With the exception. Chemical properties write down the first reaction here, the addition of hydrogen. Addition of hydrogen, write down. Catalytic hydrogenation of alkynes. Catalytic hydrogenation of alkynes. Alkynes gives alkene first. Gives alkene first. Gives alkene first. Which further goes under hydrogenation reaction and forms alkene. So, first alkene and then alkene. Eventually you will get alkene if you have sufficient hydrogen atom present. Suppose the reaction is RC, triple bond C, R dash on hydrogenation H2 with a catalyst. First it converts into an alkene which is RC double bond C, RC HC double bond at R dash. This further goes under hydrogenation reaction and eventually you get RC H2, C H2 R dash. So, alkene first and then alkene. This reaction we have already seen in the preparation of alkynes and alkene. H2 with nickel platinum catalyst what it forms. Or addition of H2 with NK in liquid NH3. Two different reactions we have. This gives you NN liquid NH3, gives you trans alkene and this gives you cis alkene. We have discussed this. Which one is bulge and which one is other one? Why have bulge reduction is different. It's not bulge reduction. This one is bulge. This one is bulge. This one is subartial sedentary reduction. What is alkene? See we have discussed. So we discussed the alkene. This is alkene to alkene. It's alkene. So alkene converts into alkene directly. Because there is only one pi bond. Here we have two. So in the first step one pi bond breaks, gives you alkene and then it converts into alkene. So if I give it enough energy will it's like the alkene point? No. If you have enough number of H2, X of H2, you will get alkene. If it is only one more, then there is no alkene. Okay. Next reaction write down. Electrophilic addition reaction. Electrophilic addition reaction. In this the first reaction we write down. Addition of X2 halogens. Addition of halogens we write down. Generally, bromination and chlorination we will discuss here. Write down. Addition of halogens. Electrophilic addition. Okay. The type of reaction is electrophilic addition. The first one is addition of halogens. Addition of halogens. Addition of halogens on alkynes gives 1,1. Gives 1,1. 2,2. Tetrahaloalkane. 1,1. 2,2. Tetrahaloalkane. This reaction involves a 3-membered cyclic-halonium ion. This reaction involves a 3-membered cyclic-halonium ion which is very unstable. Strain the rank forms hence it is unscathed. Okay. So overall the reaction is what? Suppose you have an alkene R Comes C triple bond C R dash with X2. It gives R C X2 C X 2 R dash. 2 molecules of this. It is not the domain whichever number this 1 and 2 position okay. So you see in this the intermediate step is this rc triple bond cr dash and this is a tendency to join with to join with the hellenium ion that is expressed like this it forms. This pi bond won't be there it forms a you can write like this right so three member ring. Now the point is this cyclic three member ring is highly unstable because of high angle strength three member ring high angle strength is there. So this is highly unstable. Second point is what this pi electron here the pi electron is bonded with sp hybridized nucleus of this carbon atom. That's why this pi bond is strongly bonded to these two carbon atoms and that's why what happens the reaction rate is extremely slow okay. The reaction goes with very slow rate two reason one is what highly unstable intermediate is forming which is this and the pi bond here it is connected to or joined with sp hybridized nucleus of the carbon atom which is very very you know tightly bonded there right the pi electron that's why the tendency itself to form this three member ring is less hence later of the reaction is very slow right. So since it's sp won't there be like a really large concentration of electrons so the positive highlight will like get really very strong right additional reaction takes place because of pi electron only benzene to be the same thing we have since the pi electrons are delocalized over the ring right benzene cutting suppose here this pi electrons continuously moving right because of this electron cloud only any electrophile is directed towards this so electrophile addition and that is because of the weakly bonded pi electron okay in general we say because pi bonds are weaker than the sigma bond right but here what happens if you compare alkene and alkyne of the reaction okay alkyne means the rate is extremely slow because the carbon atom is sp hybridized see this these things are relative as a means when we say that it is rate of reaction is very slow it means in comparison to alkene it is because it's three member ring three member ring so here we have a very high angle straight because of that this three member ring is highly unstable and transcendence to convert into larger member ring three to four four to five okay so two reasons first is this and the second thing is sp hybridized carbon atom the rate of the reaction is extremely slow hence the reaction is catalyst which actually enhance the rate of the reaction okay so right on this point these two reason you write down the pi electron in alkyne the pi electron in alkyne is bonded with sp hybridized carbon atom which is which is strongly held by the carbon nucleic hence the rate of the reaction is extremely slow and usually the reaction is carried out in presence of a catalyst in presence of the catalyst okay so her product is what just this pi bond we have to remove and you have to attach to hydrogen atom so this a step by step process is here also one thing you have to memorize that if you take only one mole of halogen then we'll take what then we'll have one two dihalo compound we get with one mole of hydrogen atoms so suppose the reaction is we have a c h triple bond c h ethyne and when this is allowed to react with cl2 the product is c h cl double bond c h cl with one more this is the product again if you add cl2 then the product is c h cl2 c h cl2 okay two step process or if you directly out right here excess of cl2 then this converts into okay next point right now addition of hx halogen acid second reaction first one is this addition of hx in this one in this one it is the same side side no it's like it is anti opposite side first we'll get that ring and then opposite cl attack and nothing okay we'll get a ring first see actually this gives you cl plus okay and this pi electron attack onto this so this carbon forms a three-member ring and then the other cl-lattack from the opposite side in this program that is anti-attack okay next right now addition of hx the reactivity of hydrogen halide towards alkene is this h i maximum h p r h cl and h f because of bond length here the bond length is maximum hence the dissociation is easy okay write out this reaction follows marconi cough rule this reaction follows marconi cough rule marconi cough rule so what about in the presence of peroxide same thing anti marconi cough everything is same all this therefore are very similar so the reaction of suppose c h triple bond c h with h i or if i write down c s3 c triple bond c h h i what is the product we get in this reaction so is that excessive actually okay let me write down excess it exists here also it is excess what is the product here so this is c h and i rise on the c side this one is right marconi cough rule this one with right marconi cough rule h br and peroxide the product is c s3 c s2 we are it means it is excess if it is not then we get our bond here it is anti marconi peroxide is there if it is not excess then okay see uh step by step we get this c s3 c h double bond c h br with one yes now again this one with h br correct so which carbon is more substituted which carbon is more substituted why this one why not this one this carbon is one we tell you and one hydrogen right this carbon has one hydrogen one bromide so but what counts is no you see uh br minus has tendency to attach since it is peroxide so this will attach on the carbon which has more number of hydrogen or if peroxide is not there then more substituted carbon atom since it is peroxide alkyl substituted carbon atom which you have is considered to be the more substituted one alkyl substituted so this one is the less substituted and we are will attach it discuss always you consider this that whenever we talk about substitution at the double bonded carbon atom it means alkyl substitution presence of alkyl group at the carbon atom okay so this is more substituted than this product will be br2 will attach okay in presence of peroxide if it is not there peroxide then here we'll have c br2 c s3 okay next reaction let us see uh i'll write down one more thing here similar kind of reaction alkyne shows shows with h o x okay or if you take h2 s o 4 similar kind of reaction or even if you have c s3 c o o h you just need to find out the negative part of this reagent and the positive part what is the negative part here this is the negative part which minus because oxygen is more electronegated no no addition is similar to this anti-mariconic of the negative part is that the negative part will attach and more substituted carbon atom so fluorine would be negative that is no no no no even yeah h o fluorine bond is not there it is difficult to break that bond so h o c l or h o b are generally additional reaction it shows so that was fluorine isn't h o f the only compound where fluorine has a positive thing or something you know fluorine all of which was minus there isn't even one jump out that is no that's not oxygen there's one fluorine oxygen is plus this is minus oxygen is plus fluorine is minus so with this one fluorine compound only one where fluorine has a positive yeah oxygen is the one compound here you wear the oxygen has positive because fluorine is the most negative so yes it always have minus exception is this in this compound oxygen atom is the only compound where oxygen atom is plus ok so here what happens if you have h o x that h o minus and x plus which will attach onto the carbon atom in case of h 2 s 4 what happens h plus and h s 4 minus here what happens is h plus and c s 3 c o o minus all these addition takes place according to this ok suppose my reaction c h 3 c triple bond c h with c s 3 c o h which one yes i minus plus b r minus h plus c l minus h plus what is the negative part of this reagent c s 3 c o o minus c o c double bond o c s 3 double bond c h 2 you were in the first step in the second step what happens again the same molecule c s 3 c o o h so it forms c s 3 c o c double bond o c s 3 here also we have same thing the similar exactly same pattern we have c s 3 c o o h let's do a supporter entrance it's h o x h o f