The reaction strategy is a ready, pre-set strategic solution to the potential change in the business environment

While an emergency strategy is an unforeseen emergency activity with no alternatives to meet unexpected environmental changes

Henry Mintzberg’s model of strategy can provides answer to you question as in the attached figure. It represents the difference between Intended and Emergent Strategies.

Dear 

See the link below also:

http://yourbusiness.azcentral.com/difference-between-proactive-reactive-business-strategy-13780.html

An intended strategy is a strategy that an organization hopes to execute. Intended strategies are usually described in detail within an organization’s strategic plan..An emergent strategy is an unplanned strategy that arises in response to unexpected opportunities and challenges

Dear Tomas, thanks for your input. But the question is the difference between Reactive (not intended) and Emergent strategy.

Firms have learned to analyze their competitive environment, define their position, develop competitive and corporate advantages, and understand threats to sustaining advantage in the face of challenging competitive threats. Different approaches including industrial organization, the resource-based view, dynamic capabilities, and game theory have helped academicians and practitioners understand the dynamics of competition and develop recommendations on how firms should define their competitive and corporate strategies. However, drivers such as globalization, deregulation, or technological change, just to mention a few, are profoundly changing the competitive game. 

http://docplayer.net/37767278-From-strategy-to-business-models-and-to-tactics.html

Reactive business strategies are those that respond to some unanticipated event only after it occurs (by Scott Thompson), while on the other hand, a strategy can be described as emergent where consistencies arise in the actions / behavior of an organization over a period of time, even though the adoption of such behavior / actions was never explicitly intended; an example of this can occur ‘when an environment directly imposes a pattern of action on an organization (by Adewale Manuwa).

http://smallbusiness.chron.com/difference-between-proactive-reactive-business-strategy-62157.html

https://www.linkedin.com/pulse/20140630061420-296333353-deliberate-vs-emergent-business-strategy

An emergent strategy, though never explicitly intended as such is still a novel and consistent plan of action to create a market /attain profits or otherwise tackle unique business problems. IT is no longer mandatory that these be guided by the environment and can refer to any recognised aspect of the organization and its dynamics handled by the strategy. It may just be an undocumented strategy till its recognized in a specific organization as a planned response, it may however be causated by a reaction to market forces in the bid to gain the specified competitive advantage (in a specific product market like automobile markets in Asia). China's bid to copy western technology through force of policy as also domestic market regulations may have causated a dozen unique emergent strategies in that industry in China leading to new winners even before their planned global inorganic expansion

A reactive strategy true to its name is just a strategy to regain ground from reversals due to a market phenomenon, including competitive actions or environmental forces (like the rollout of GST may lead to change in distribution structures both reactively and emergently)

Dear Debi,

I once made a model of difference between reactive and emergent strategies (see enclosed). Reactive strategy in this model are firm's actions when the performance falls to the  level which is no longer accepted by at least one of the major stakeholders (shareowners, customers, employees, suppliers). Emergent strategies are actions to meet new hardly anticipated events (both negative and positive ones).

bests,

Igor Gurkov

Article Explaining the “Ilya Muromets Syndrome” of Business Innovati...

Dear Sir,

Proactive business strategies are used to achieve predetermined goals. For instance, a proactive marketing strategy carries out research, development and promotional objectives for your business.

Reactive strategy doesn't mean your business waits for crises to plan. Instead, you develop a strategy with more of a wait-and-see approach.

Reactive strategy in this model are firm's actions when the performance falls to the level which is no longer accepted by at least one of the major stakeholders (shareowners, customers, employees, suppliers). Emergent strategies are actions to meet new hardly anticipated events (both negative and positive ones).

Reactive strategy in this model are firm's actions when the performance falls to the level which is no longer accepted by at least one of the major stakeholders (shareowners, customers, employees, suppliers). Emergent strategies are actions to meet new hardly anticipated events (both negative and positive ones).

https://www.differencebetween.com/category/business/management/strategy-business/

Reactive business strategies are aimed at providing a response to unexpected changes or events without any extra initiative and implementing strategic plans for sustainable growth while An emergent strategy is one that arises from unplanned actions and initiatives within an organization.