reagents usedto make detergent

the difference comes from the raw materials used.

for alkylbenzenesulfonates, raw material is alkylbenzene, and sulfonation occurs on the benzene ring.
mechanism of sulfonation on benzene involves addition of SO3 (dissolved in / formed by conc. H2SO4).
in the reaction, the carbon on benzene is directly attached on the S-atom, not the O-atom. thus, there's only C-S bond, not C-O-S bond.

(this's electrophilic aromatic substitution, involving benzene ring).


for alkylsulfate, common raw material is long-chain alcohol / alkanol and sulfuric acid (H2SO4). halosulfuric acid (XSO3H, X can be Cl.. chlorosulfuric acid) are also used.
mechanism of formation of akylsulfate involves attachment of alkanol's O-atom onto sulfuric acid's S-atom, forming an S-O bond which links alkyl and sulfate. water or HCl is removed.
in the reaction, the carbon on alkanol does NOT directly attach on S-atom. thus there's C-O-S bond but not C-S bond.

(in terms of organic chemistry, it's sort of esterification.. but never mind)



it's good for you to notice the difference between sulfonate and sulfate.
consider also other raw materials required for reactions.
you may not be familiar with the mechanisms. if you're interested, i can show you some of this ---- though it's probably not examined in your syllabus.


2011-06-02 21:27:50 補充：
Re: Wai Ho,
1. alcohol is ONE of the possible raw materials. alkene is also possible.
for alkene, H on acid goes to one of the C=C carbon, while the O on H2SO4 that loses H goes to another carbon on C=C. the O in C-O-S comes from sulfuric acid.

2011-06-02 21:30:26 補充：
how about alcohol? well, according to the mechanisms, there're two possible ways for sulfuric acid to react with alcohol. the O in C-O-S bond can either come from alcohol or acid, so it's difficult to decide.

this has to be determined experimentally; i suspect that both cases are do-able.

2011-06-02 21:33:17 補充：
2.
this is NOT considered hydrolysis. in hydrolysis, there's fragmentation of large molecule, giving two or more small fragments.
both sulfonic acid and (alkyl-)sulfuric acid are strong acids. NaOH acts to neutralize the acid, producing the long-chain anions (responsible for cleaning ability).

2011-06-02 21:35:42 補充：
3.
you may say so.
but the equation actually is showing the conversion of the species that we're interested; what we're interested is the organic part, not the counter-ion.

we can also use alkali other than NaOH, like we can use KOH or NH3, producing potassium salt and ammonium salt.

2011-06-02 21:36:22 補充：
properties of the detergent made would have some difference when compared to the sodium salt.

then why
同樣H2SO4 有 一SO3H group 同 一OSO3H group
點分

Incase 1, when H2SO4 is added, -SO3H is formed.Then, NaOH converts -SO­3H to -SO3⁻ion.

In case 2, when H2SO4 is added, -OSO3H isformed. Then, NaOH converts -OSO3H to -OSO3⁻ ion.