Without looking them up, rank the following compounds in decre...

Question

Without looking them up, rank the following compounds in decreasing order of acidity. These examples represent large classes of compounds that differ widely in acidity.

water, ethanol, 2-chloroethanol, tert-butyl alcohol, ammonia, sulfuric acid, hexane, hex-1-yne, acetic acid

Accepted Answer

All right. Hi, everyone. So this question is asking us considering their structures and relative PK values rank following. In order of increasing acidity. Here we have Seburo alcohol, water, propan 102 chloral propan 10 propo acid, nitric acid, Hept, one iron hept and methyl amine. So let's start by drawing out each of our structures starting off with sebu alcohol. The phrase beetle indicates that our parent chain is four carbons long and the prefix suck here as in S sebu alcohol means that a hydroxy group is attached to a secondary carbon of the parent chain. Up. Next we have water which is H2O. Then we have propan 10 which is a three carbon parent chain and a hydroxy group on carbon number one. Then we have two chloral propane, one all which is another three carbon chain, the hydroxy group on carbon number one. But this time theres an atom of chlorine on carbon number two of the parent chain. Next off we have propo OIC acid which is a carboxylic acid. So that's a three carbon chain. And at the very end on carbon number one is both a hydroxy group and a carbonel. Now recall that nitric acid has a molecular formula of HNO three which is an atom of nitrogen in the center having one double bond to an oxygen atom, a single bond to another oxygen atom with a negative charge and another single bond to a hydroxy group. This gives nitrogen a positive charge up. Next is hept one I which is a seven carbon parent chain and an all kind or a triple wand in between carbons. One and two, two more left we have heptane which is a seven carbon Alcaine. So only single bonds in between carbons and then we have methyl amit. Now recall that amines have a general formula of NR three in which R can symbolize either hydrogen or an oyo group. In this case, we have only one group which is a metal group or a CH three. So that becomes CH three NH two. All right. So now let's go ahead and talk about PK recall that Pka is a measure of a particular compound acidity. And it follows the same logic as the PH scale which means that the smaller the PK value is the more acidic that substance happens to be. Now, the known strong acids are those that are remarkably strong le acidic because of the fact that they have negative PK values. An example of these known strong acids is nitric acid. So because nitric acid is known to have a very high or sorry, very low negative PK value. Nitric acid is going to be the strongest on our list. So from here, let's compare relative PK values based on what functional groups are present. First off, we have alcohol or excuse me, water that has a PK of about 15.7 or carboxylic acid propo OIC acid would have a PK of about five have one in being a terminal all kind would have a PK of about 25 methyl amine being an amine would have a PK of about 38 and Hept being an all cane would have a PK of about 50. So our alcohols on the other hand, tend to have PK values ranging between 16 through 18. So before we go ahead and talk about our three alcohols in a bit more detail, I want to first point out that Hept with the largest PK value of all the compounds that we're considering would be the weakest asset. And just before hept would be methyl amine. On the other hand, propo OIC acid would be the second strongest. So that means methyl amine would be the second weakest. But now lets talk about our alcohols in a bit more detail and also where water is going to be ranked among this comparison because recall that water having a PK of 15.7 tends to be more acidic than most alcohols. However, when we look at two chloral propane, 10 two chloral propane, 10 has a chlorine atom adjacent to the hydroxy group, which is an electron withdrawing group due to its high electronegativity. Recall that the presence of in of an electron withdrawing substituents such as the halogen here actually increases the acidity of the compound in question. So because of this, the hydroxy group of two chlor propane 10 is made more acidic than water. So from here that leaves us to compare seburo alcohol and propan one, all recall that Oyo groups, by contrast, are considered electron donating groups which actually decrease acidity. So the more electron donating groups are present surrounding that hydroxy group, the less acidic it happens to be. So tertiary alcohols are the least acidic followed by secondary alcohols and finally followed by primary alcohols. So here because Propan won all is a primary alcohol and sec butto alcohol is a secondary alcohol propane one, all it is more acidic than seburo alcohol. So now let's go ahead and organize our answer. In order from least acidic to most acidic, the least acidic as discussed previously would be hept with the highest PK value 50 followed by methyl amine with a PK of 38 and then followed by hat 19 with a PK of 25. So from here, I would go ahead and place Seburo alcohol which was less acidic than propane. One. All from here, we have water and then we have two chloral propane. One. All this leaves us now with our two strongest, which is propo OIC acid followed by our strongest, which is nitric acid and there you have it. So here is our complete ranking. So with that being said, thank you so very much for watching and I hope you found this helpful.

Without looking them up, rank the following compounds in decreasing order of acidity. These examples represent large classes of compounds that differ widely in acidity.
water, ethanol, 2-chloroethanol, tert-butyl alcohol, ammonia, sulfuric acid, hexane, hex-1-yne, acetic acid

Key Concepts

Acidity and pKa

Functional Groups and Their Influence on Acidity

Comparative Acidity of Common Compounds

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