Very little of the content was changed. There is one section on TLC co-spots that was broken into 2 sections, a few more “safety notes” were added, but otherwise the order and content is nearly identical to the 1st edition. The majority of the 2nd edition changes had to do with formatting:
An expanded table of contents was added.
The second edition is more print-friendly: page numbers were added to all table of contents and margins were enlarged to allow for better front-back printing.
The section numbering was reevaluated.
Major work was done to make the textbook more accessible: images were consolidated and provided with alt-texts for electronic screen readers. Color contrast was also improved in some areas (at least for the e-book, I am not sure about printed contrast), and formatting was in general cleaned up.
For fun, more student pictures were added from Spring 2017’s group of o-chem!
Image resolution was upgraded, which resulted in a larger final product (113 MB), but in my opinion improved the quality.
Copyright was modified in a minor way, stating that academic bookstores may print the textbook for a small profit (see page 12).