The rate of decomposition of s-butyl nitrite (SBN) has been studied in the absence (130-160Β°C) and presence (160-200Β°C) of NO. Under the former conditions, for low concentrabions of SBN (6 x 10-5 -lO-4M) and small extents of reaction (-l.5yc), the first-order homogeneoris rates of acetaldehyde (AcH) formation are a direct measure of reaction (1) since k 3 , >> k 2 ( N O ) : SBN &s-BuO + NO, s-Bui) -% AcH + c t . Unlike I-butyl nit.rite (TBN), d(AcH)/dt is independent of added CFa (-0.9 atni). Thus k ~, is always >> k,(NO) over this pressure range. Large amounts of NO (-0.9 atm) (130-16OoC) completely suppress AcH formation. k , = 1016.*-400.Q/0 aec-1. Since (El + 127') and AH', are identical, wit.hin experimental error, both may be equated with D(S-BUO-NO) = 41..i f 0.8 kcal/niol and E , = 0 i 0.8 kcal/niol. The therniochemistry leads to the result AH", (s-BuO) = -16.6 j , 0.8 kcal/mol. From ASo, and A , , k2 is calculat.ed to be 1010.4 M-' . sec-l, identical t o that for TBN. From an independent observation that k6/k, = 0.26 0.01 independent of temperature, s-Bui) + NO M E K + HNO, we find E6 = 0 & 1 kcal/mol and k, = I O 9 . S W L . sec-1. Under the conditions first cited, methyl ethyl ketone (MEK) is also a product of the reaction, t.he rate of which beconies measurable at extents of conversion >2:';. trowever, this rate is -0.1 that of AcH formation. Although MEK formation is affected by the ratio S / V for different reaction vessels, in a spherical reaction vessel, this 1IEK arises as Lhe result of an essentially homogeneous first.-order 4-centre elimination of HNO. SBN M E K + HNO; k , == 1012.*-35.*/8 sec-1. Sec-butyl alcohol (SBA), formed a t a rate compar:ible to MEK, is thought to arise via the hydrolysis of SBPU' , the water being formed from HNO.
The rate of disappearance of SBN, that is, d(MEK + SBA + AcH)/dt, is given by kglohnl = 10L5.7-39.6/0 sec-l. I n NO (-1 a t m ) the rate of formation of 1IKK was about twice that in the absence of NO, whereas the SB.4 was greatly reduced. This reaction was also affected by the r:itio S / V of different reaction vessels. It was again concluded that in a spherical reaction vessel, the rate of M E K formation was essentially honiogeneoos and first, order. This r:ite is given by kobs = 1012.Q-35 " 8 sec-', very similar to k5. However, although i t is clear t h t , the rate of formation of M E K is doubled in the presence o f NO, the value for k,br makes it difficult to associate this extra MKK with thedisproportionation of s-BuQ and NO: s-Bid) + N O -% M E K + HNO. NO a t temperatures of 1 3 0 -1 6 0 ~~ completely suppresses A ~H format ion. A4cH reappears a t higher temperatures (16j-20OoC), enabling k3. to be determined.
Ignoring r e a d o n ( G ) , d(AcIl)/dL = k,ks (m)/[k3, + k,(NO)j; k a c = 1014,S-L5.3/8 sec-l.
Inclusion of reaction (6) into the mechanism makes very little difference to t.he resrilt. Reaction ( 3 c ) is expected to be a pressure-dependent process.