greenimp - 20-5-2009 at 10:10
From Organic Syntheses link
The part that I think is wrong is below. they are doing a Hoffman rearrangement on veratric amide using Sodium hypochlorite and NaOH. They are
preparing their hypochlorite fresh before use from Cl2 (g).
My problem is it looks like they are not generating enough hypochlorite. The call for 0.412 g per gram of amide. My math works this out to .33 Moles
of Cl2 for .32 M of amide (a 5% excess is said to be used, which makes sense) However, this much Cl2 gas should only produce .11 M of hypochlorite,
when .33 M of hypochlorite is desired.
Anyway, I think they messed up their calculations. The problem is that I think if one where to use the correct amount of gas, there would be almost no
NaoH left in the inital solution. There need to be NaOH in there to initiate the Hoffman.
Here is the paragraph in question.
An alkaline solution of sodium hypochlorite is prepared by passing chlorine (0.412 gram for each gram of the amide) (Note 2) into a mixture of 300 g.
of cracked ice and a cold solution of 80 g. of sodium hydroxide in 500 cc. of water, contained in a 2-l. round-bottomed flask. The whole of the
veratric amide (55–58 g.) is added in one portion, and the mixture is warmed slowly in a water bath, with mechanical stirring. The material soon
darkens in color, and at 50–55° (internal temperature) oily droplets begin to separate. The temperature is raised gradually to 70° and maintained
at this point for one hour. A solution of 120 g. of sodium hydroxide in 120 cc. of water is added slowly, and the temperature is increased to 80° for
an additional hour.
I think it should read:
An alkaline solution of sodium hypochlorite is prepared by passing chlorine (1.236) gram for each gram of the amide) (Note 2) into a mixture of 300 g.
of cracked ice and a cold solution of 135 g. of sodium hydroxide in 500 cc. of water, contained in a 2-l. round-bottomed flask. The whole of the
veratric amide (55–58 g.) is added in one portion, and the mixture is warmed slowly in a water bath, with mechanical stirring. The material soon
darkens in color, and at 50–55° (internal temperature) oily droplets begin to separate. The temperature is raised gradually to 70° and maintained
at this point for one hour. A solution of 120 g. of sodium hydroxide in 120 cc. of water is added slowly, and the temperature is increased to 80° for
an additional hour.
GI
Polverone - 20-5-2009 at 11:13
One mole of veratric amide is 181.17 grams. One mole of Cl2, which gives rise to 1 mole of NaOCl in NaOH solution (how did you come up with 1/3?), is
70.91 grams. 70.91/181.17 gives 0.391 grams of chlorine per gram of amide, or with a 5% excess, 0.412 just like Org Syn says.
greenimp - 20-5-2009 at 12:21
3 Cl2 + 6 NaOH → 5 NaCl + NaClO3 + 3H2O
I thought this was the formula for Sodium hypochlorite formation from chlorine gas and NaOH.
If I am wrong that would explain my problem.
The_Davster - 20-5-2009 at 12:31
That is the equation for sodium chlorate formation...
greenimp - 20-5-2009 at 12:38
oh shit. 
Its this one: Cl2 + 2 NaOH -> NaClO + NaCl + H20
That's what I get for not reading more carefully...everything makes perfect sense now.
[Edited on 20-5-2009 by greenimp]