Determination of the pKa of cyclobutanone: Brønsted correlation of the general base-catalyzed enolization in aqueous solution and the effect of ring strain.

The induction of strain in carbocycles, thereby increasing the amount of s-character in the C-H bonds and the acidity of these protons, has been probed with regard to its effect on the rate constants for the enolization of cyclobutanone. The second-order rate constants for the general base-catalyzed enolization of cyclobutanone have been determined for a series of 3-substituted quinuclidine buffers in D(2)O at 25 °C, I = 1.0 M (KCl). The rate constants for enolization were determined by following the extent of deuterium incorporation (up to ∼30% of the first α-proton) into the α-position, as a function of time. The observed pseudo-first-order rate constants correlated to the [basic form] of the buffer and yielded the second-order rate constants for the general base-catalyzed enolization of cyclobutanone for four tertiary amine buffers. A Brønsted ß-value of 0.59 was determined from the second-order rate constants determined. Comparison of the results for cyclobutanone to those previously reported for acetone and a 1-phenylacetone derivative, under similar conditions, indicated that the ring strain of the carbocycle appeared to have only a small effect on the general base-catalyzed rate constants for enolization. The similarity of the rate constants for the general base-catalyzed enolization of cyclobutanone to those determined for acetone allowed for an estimation of the limits of the rate constant for protonation of the enolate intermediate of cyclobutanone by the conjugate acid of 3-quinuclidinone (k(BH) = 5 × 10(8) - 2 × 10(9) M(-1) s(-1)). Combining the rate constants for deprotonation of cyclobutanone (k(B)) and protonation of the enolate of cyclobutanone (k(BH)) by 3-quinuclidinone and its conjugate acid, the pK(a) of the α-protons of cyclobutanone has been estimated to be pK(a) = 19.7-20.2.

Upper limb function and brain reorganization after constraint-induced movement therapy in children with hemiplegia.

OBJECTIVE: The aims of this study were to (1) investigate the effectiveness of CIMT for children with hemiplegia, (2) determine the feasibility of using fMRI for describing brain activity patterns before and after CIMT and (3) describe changes in brain reorganization after CIMT in children with hemiplegia using fMRI. DESIGN: Before and after study with one group. METHODS: Ten children aged 7-14 years (M = 11.0, SD = 2.5) with hemiplegia received CIMT over a 2-week period using a before and after design. Clinical measures included the Melbourne Assessment of Unilateral Upper Limb Function, upper limb kinematics and parent questionnaire. Children were measured with fMRI before and after CIMT. RESULTS: Findings showed that CIMT may be effective at improving upper limb function in some, but not all children; those children with a moderate degree of impairment seemed to benefit the most. fMRI findings correlated moderately with clinical measures. CONCLUSION: Although unique challenges with fMRI data collection exist for this population, it provides potentially valuable information to better understand mechanisms of change after interventions such as CIMT.

Modified constraint-induced movement therapy for a 12-month-old child with hemiplegia: a case report.

OBJECTIVE: This case report describes the use of modified constraint-induced movement therapy (CIMT) to improve upper-limb function in a 12-month-old child with right hemiplegia. It also describes parent concerns about CIMT and documents the short- and long-term effects of modified CIMT. METHOD: The participant was assessed 5 times over a 7.5-month period using the Peabody Developmental Motor Scales-2, Pediatric Motor Activity Log, Toddler Amount of Use Test, and Knox Parent Questionnaire. CIMT included a nonremovable cast worn on the unaffected arm and approximately 8 hr per week of occupational and physical therapy for 2 weeks. RESULTS: Benefits of improved upper-limb function measured immediately after CIMT were sustained at 6 months' follow-up. No adverse events related to cast use were reported. DISCUSSION: The findings from this case report suggest that CIMT was a safe intervention associated with improving upper-limb function for this young child with hemiplegia.